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 $92.46   5.620%   $97.6563   $97.66   $97.65   $97.70  
  Purchase #2 $216.29   4.593%   $226.2242   $226.22   $226.20   $226.20  
  Purchase #3 $43.84   10.527%   $48.455   $48.46   $48.45   $48.50  
  Purchase #4 $110.70   5.471%   $116.7564   $116.76   $116.75   $116.80  
  Purchase #5 $132.35   12.178%   $148.4676   $148.47   $148.45   $148.50  
  Purchase #6 $58.59   9.254%   $64.0119   $64.01   $64.00   $64.00  
  Purchase #7 $210.94   7.472%   $226.7014   $226.70   $226.70   $226.70  
  7 purchase totals = $865.17       $928.2728   $928.28   $928.20   $928.40