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 $58.44   10.141%   $64.3664   $64.37   $64.35   $64.40  
  Purchase #2 $58.98   11.447%   $65.7314   $65.73   $65.75   $65.70  
  Purchase #3 $79.47   6.331%   $84.5012   $84.50   $84.50   $84.50  
  Purchase #4 $228.57   3.227%   $235.946   $235.95   $235.95   $235.90  
  Purchase #5 $53.98   5.819%   $57.1211   $57.12   $57.10   $57.10  
  Purchase #6 $193.28   9.595%   $211.8252   $211.83   $211.85   $211.80  
  Purchase #7 $40.40   7.791%   $43.5476   $43.55   $43.55   $43.50  
  7 purchase totals = $713.12       $763.0389   $763.05   $763.05   $762.90