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 $216.74   9.192%   $236.6627   $236.66   $236.65   $236.70  
  Purchase #2 $131.60   12.182%   $147.6315   $147.63   $147.65   $147.60  
  Purchase #3 $38.73   12.103%   $43.4175   $43.42   $43.40   $43.40  
  Purchase #4 $228.33   7.766%   $246.0621   $246.06   $246.05   $246.10  
  Purchase #5 $96.83   11.300%   $107.7718   $107.77   $107.75   $107.80  
  Purchase #6 $228.35   8.395%   $247.52   $247.52   $247.50   $247.50  
  Purchase #7 $72.33   7.185%   $77.5269   $77.53   $77.55   $77.50  
  7 purchase totals = $1,012.91       $1,106.5925   $1,106.59   $1,106.55   $1,106.60