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 $227.74   3.158%   $234.932   $234.93   $234.95   $234.90  
  Purchase #2 $96.29   5.338%   $101.43   $101.43   $101.45   $101.40  
  Purchase #3 $72.25   4.777%   $75.7014   $75.70   $75.70   $75.70  
  Purchase #4 $100.90   4.217%   $105.155   $105.16   $105.15   $105.20  
  Purchase #5 $82.66   4.767%   $86.6004   $86.60   $86.60   $86.60  
  Purchase #6 $226.82   5.212%   $238.6419   $238.64   $238.65   $238.60  
  Purchase #7 $95.76   6.532%   $102.015   $102.02   $102.00   $102.00  
  7 purchase totals = $902.42       $944.4757   $944.48   $944.50   $944.40