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 $34.34   10.507%   $37.9481   $37.95   $37.95   $37.90  
  Purchase #2 $228.43   13.273%   $258.7495   $258.75   $258.75   $258.70  
  Purchase #3 $226.61   6.446%   $241.2173   $241.22   $241.20   $241.20  
  Purchase #4 $181.30   3.108%   $186.9348   $186.93   $186.95   $186.90  
  Purchase #5 $54.87   13.594%   $62.329   $62.33   $62.35   $62.30  
  Purchase #6 $25.54   7.278%   $27.3988   $27.40   $27.40   $27.40  
  Purchase #7 $126.93   7.574%   $136.5437   $136.54   $136.55   $136.50  
  7 purchase totals = $878.02       $951.1212   $951.12   $951.15   $950.90