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 $184.86   8.763%   $201.0593   $201.06   $201.05   $201.10  
  Purchase #2 $52.34   6.315%   $55.6453   $55.65   $55.65   $55.60  
  Purchase #3 $143.98   6.520%   $153.3675   $153.37   $153.35   $153.40  
  Purchase #4 $131.56   3.863%   $136.6422   $136.64   $136.65   $136.60  
  Purchase #5 $166.95   13.722%   $189.8589   $189.86   $189.85   $189.90  
  Purchase #6 $180.68   12.137%   $202.6091   $202.61   $202.60   $202.60  
  Purchase #7 $180.71   8.436%   $195.9547   $195.95   $195.95   $196.00  
  7 purchase totals = $1,041.08       $1,135.1370   $1,135.14   $1,135.10   $1,135.20