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 $83.51   13.702%   $94.9525   $94.95   $94.95   $95.00  
  Purchase #2 $178.73   10.470%   $197.443   $197.44   $197.45   $197.40  
  Purchase #3 $250.35   4.471%   $261.5431   $261.54   $261.55   $261.50  
  Purchase #4 $89.53   9.633%   $98.1544   $98.15   $98.15   $98.20  
  Purchase #5 $107.69   8.502%   $116.8458   $116.85   $116.85   $116.80  
  Purchase #6 $13.60   8.566%   $14.765   $14.77   $14.75   $14.80  
  Purchase #7 $162.52   8.322%   $176.0449   $176.04   $176.05   $176.00  
  7 purchase totals = $885.93       $959.7487   $959.74   $959.75   $959.70