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 $59.53   9.109%   $64.9526   $64.95   $64.95   $65.00  
  Purchase #2 $65.81   4.770%   $68.9491   $68.95   $68.95   $68.90  
  Purchase #3 $141.38   10.186%   $155.781   $155.78   $155.80   $155.80  
  Purchase #4 $174.71   7.489%   $187.794   $187.79   $187.80   $187.80  
  Purchase #5 $188.74   3.603%   $195.5403   $195.54   $195.55   $195.50  
  Purchase #6 $191.99   12.365%   $215.7296   $215.73   $215.75   $215.70  
  Purchase #7 $32.36   13.824%   $36.8334   $36.83   $36.85   $36.80  
  7 purchase totals = $854.52       $925.5800   $925.57   $925.65   $925.50