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 $60.25   4.575%   $63.0064   $63.01   $63.00   $63.00  
  Purchase #2 $136.41   11.685%   $152.3495   $152.35   $152.35   $152.30  
  Purchase #3 $101.89   6.190%   $108.197   $108.20   $108.20   $108.20  
  Purchase #4 $22.55   9.574%   $24.7089   $24.71   $24.70   $24.70  
  Purchase #5 $52.29   5.148%   $54.9819   $54.98   $55.00   $55.00  
  Purchase #6 $30.38   9.209%   $33.1777   $33.18   $33.20   $33.20  
  Purchase #7 $189.95   13.563%   $215.7129   $215.71   $215.70   $215.70  
  7 purchase totals = $593.72       $652.1343   $652.14   $652.15   $652.10