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 $57.92   9.201%   $63.2492   $63.25   $63.25   $63.20  
  Purchase #2 $213.64   7.474%   $229.6075   $229.61   $229.60   $229.60  
  Purchase #3 $148.78   6.872%   $159.0042   $159.00   $159.00   $159.00  
  Purchase #4 $88.68   5.266%   $93.3499   $93.35   $93.35   $93.30  
  Purchase #5 $200.66   12.676%   $226.0957   $226.10   $226.10   $226.10  
  Purchase #6 $57.93   5.234%   $60.9621   $60.96   $60.95   $61.00  
  Purchase #7 $115.39   4.165%   $120.196   $120.20   $120.20   $120.20  
  7 purchase totals = $883.00       $952.4646   $952.47   $952.45   $952.40