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 $144.46   5.605%   $152.557   $152.56   $152.55   $152.60  
  Purchase #2 $62.71   5.114%   $65.917   $65.92   $65.90   $65.90  
  Purchase #3 $156.28   4.648%   $163.5439   $163.54   $163.55   $163.50  
  Purchase #4 $90.79   7.604%   $97.6937   $97.69   $97.70   $97.70  
  Purchase #5 $72.96   3.792%   $75.7266   $75.73   $75.75   $75.70  
  Purchase #6 $204.93   9.553%   $224.507   $224.51   $224.50   $224.50  
  Purchase #7 $163.25   12.708%   $183.9958   $184.00   $184.00   $184.00  
  7 purchase totals = $895.38       $963.9410   $963.95   $963.95   $963.90