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 $141.25   7.575%   $151.9497   $151.95   $151.95   $151.90  
  Purchase #2 $22.81   6.595%   $24.3143   $24.31   $24.30   $24.30  
  Purchase #3 $222.67   3.282%   $229.978   $229.98   $230.00   $230.00  
  Purchase #4 $92.53   9.660%   $101.4684   $101.47   $101.45   $101.50  
  Purchase #5 $68.34   11.793%   $76.3993   $76.40   $76.40   $76.40  
  Purchase #6 $25.66   8.254%   $27.778   $27.78   $27.80   $27.80  
  Purchase #7 $218.90   7.540%   $235.4051   $235.41   $235.40   $235.40  
  7 purchase totals = $792.16       $847.2928   $847.30   $847.30   $847.30