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 $90.95   5.502%   $95.9541   $95.95   $95.95   $96.00  
  Purchase #2 $215.98   13.372%   $244.8608   $244.86   $244.85   $244.90  
  Purchase #3 $131.28   7.483%   $141.1037   $141.10   $141.10   $141.10  
  Purchase #4 $90.50   4.649%   $94.7073   $94.71   $94.70   $94.70  
  Purchase #5 $148.93   6.674%   $158.8696   $158.87   $158.85   $158.90  
  Purchase #6 $11.53   4.301%   $12.0259   $12.03   $12.05   $12.00  
  Purchase #7 $15.42   6.600%   $16.4377   $16.44   $16.45   $16.40  
  7 purchase totals = $704.59       $763.9591   $763.96   $763.95   $764.00