Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $210.83   11.232%   $234.5104   $234.51   $234.50   $234.50  
  Purchase #2 $208.76   13.143%   $236.1973   $236.20   $236.20   $236.20  
  Purchase #3 $119.47   12.780%   $134.7383   $134.74   $134.75   $134.70  
  Purchase #4 $177.50   8.507%   $192.5999   $192.60   $192.60   $192.60  
  Purchase #5 $131.78   12.287%   $147.9718   $147.97   $147.95   $148.00  
  Purchase #6 $102.98   3.245%   $106.3217   $106.32   $106.30   $106.30  
  Purchase #7 $183.34   10.636%   $202.84   $202.84   $202.85   $202.80  
  7 purchase totals = $1,134.66       $1,255.1794   $1,255.18   $1,255.15   $1,255.10