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 $219.84   8.121%   $237.6932   $237.69   $237.70   $237.70  
  Purchase #2 $65.54   4.672%   $68.602   $68.60   $68.60   $68.60  
  Purchase #3 $94.73   7.335%   $101.6784   $101.68   $101.70   $101.70  
  Purchase #4 $137.34   3.553%   $142.2197   $142.22   $142.20   $142.20  
  Purchase #5 $238.69   11.208%   $265.4424   $265.44   $265.45   $265.40  
  Purchase #6 $23.47   9.736%   $25.755   $25.76   $25.75   $25.80  
  Purchase #7 $51.63   4.801%   $54.1088   $54.11   $54.10   $54.10  
  7 purchase totals = $831.24       $895.4995   $895.50   $895.50   $895.50