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 $146.94   3.459%   $152.0227   $152.02   $152.00   $152.00  
  Purchase #2 $179.78   13.111%   $203.351   $203.35   $203.35   $203.40  
  Purchase #3 $139.98   13.453%   $158.8115   $158.81   $158.80   $158.80  
  Purchase #4 $92.98   9.265%   $101.5946   $101.59   $101.60   $101.60  
  Purchase #5 $143.45   6.402%   $152.6337   $152.63   $152.65   $152.60  
  Purchase #6 $159.76   10.532%   $176.5859   $176.59   $176.60   $176.60  
  Purchase #7 $145.45   8.768%   $158.2031   $158.20   $158.20   $158.20  
  7 purchase totals = $1,008.34       $1,103.2025   $1,103.19   $1,103.20   $1,103.20