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 $116.85   5.699%   $123.5093   $123.51   $123.50   $123.50  
  Purchase #2 $214.82   13.314%   $243.4211   $243.42   $243.40   $243.40  
  Purchase #3 $157.92   3.176%   $162.9355   $162.94   $162.95   $162.90  
  Purchase #4 $210.98   13.813%   $240.1227   $240.12   $240.10   $240.10  
  Purchase #5 $188.78   11.420%   $210.3387   $210.34   $210.35   $210.30  
  Purchase #6 $203.87   3.490%   $210.9851   $210.99   $211.00   $211.00  
  Purchase #7 $229.77   11.226%   $255.564   $255.56   $255.55   $255.60  
  7 purchase totals = $1,322.99       $1,446.8764   $1,446.88   $1,446.85   $1,446.80