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 $58.52   6.739%   $62.4637   $62.46   $62.45   $62.50  
  Purchase #2 $82.65   5.102%   $86.8668   $86.87   $86.85   $86.90  
  Purchase #3 $115.82   10.707%   $128.2208   $128.22   $128.20   $128.20  
  Purchase #4 $215.64   8.368%   $233.6848   $233.68   $233.70   $233.70  
  Purchase #5 $74.78   4.804%   $78.3724   $78.37   $78.35   $78.40  
  Purchase #6 $88.44   7.130%   $94.7458   $94.75   $94.75   $94.70  
  Purchase #7 $243.54   7.562%   $261.9565   $261.96   $261.95   $262.00  
  7 purchase totals = $879.39       $946.3108   $946.31   $946.25   $946.40