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 $84.34   12.152%   $94.589   $94.59   $94.60   $94.60  
  Purchase #2 $146.66   5.598%   $154.87   $154.87   $154.85   $154.90  
  Purchase #3 $116.29   7.398%   $124.8931   $124.89   $124.90   $124.90  
  Purchase #4 $238.49   4.321%   $248.7952   $248.80   $248.80   $248.80  
  Purchase #5 $76.81   13.105%   $86.876   $86.88   $86.90   $86.90  
  Purchase #6 $205.75   11.396%   $229.1973   $229.20   $229.20   $229.20  
  Purchase #7 $176.46   3.121%   $181.9673   $181.97   $181.95   $182.00  
  7 purchase totals = $1,044.80       $1,121.1879   $1,121.20   $1,121.20   $1,121.30