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 $93.84   4.462%   $98.0271   $98.03   $98.05   $98.00  
  Purchase #2 $117.68   12.148%   $131.9758   $131.98   $132.00   $132.00  
  Purchase #3 $162.64   7.567%   $174.947   $174.95   $174.95   $174.90  
  Purchase #4 $76.67   12.189%   $86.0153   $86.02   $86.00   $86.00  
  Purchase #5 $51.52   6.435%   $54.8353   $54.84   $54.85   $54.80  
  Purchase #6 $103.52   11.547%   $115.4735   $115.47   $115.45   $115.50  
  Purchase #7 $143.56   7.505%   $154.3342   $154.33   $154.35   $154.30  
  7 purchase totals = $749.43       $815.6082   $815.62   $815.65   $815.50