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 $46.71   4.108%   $48.6288   $48.63   $48.65   $48.60  
  Purchase #2 $195.28   11.520%   $217.7763   $217.78   $217.80   $217.80  
  Purchase #3 $72.48   4.200%   $75.5242   $75.52   $75.50   $75.50  
  Purchase #4 $61.88   9.339%   $67.659   $67.66   $67.65   $67.70  
  Purchase #5 $170.69   4.648%   $178.6237   $178.62   $178.60   $178.60  
  Purchase #6 $169.45   10.791%   $187.7353   $187.74   $187.75   $187.70  
  Purchase #7 $11.47   9.482%   $12.5576   $12.56   $12.55   $12.60  
  7 purchase totals = $727.96       $788.5049   $788.51   $788.50   $788.50