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 $94.63   3.153%   $97.6137   $97.61   $97.60   $97.60  
  Purchase #2 $39.63   12.813%   $44.7078   $44.71   $44.70   $44.70  
  Purchase #3 $30.76   6.732%   $32.8308   $32.83   $32.85   $32.80  
  Purchase #4 $87.29   4.710%   $91.4014   $91.40   $91.40   $91.40  
  Purchase #5 $93.78   11.679%   $104.7326   $104.73   $104.75   $104.70  
  Purchase #6 $146.93   4.106%   $152.9629   $152.96   $152.95   $153.00  
  Purchase #7 $166.45   7.774%   $179.3898   $179.39   $179.40   $179.40  
  7 purchase totals = $659.47       $703.6390   $703.63   $703.65   $703.60