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 $62.26   10.396%   $68.7325   $68.73   $68.75   $68.70  
  Purchase #2 $164.99   5.665%   $174.3367   $174.34   $174.35   $174.30  
  Purchase #3 $83.93   5.403%   $88.4647   $88.46   $88.45   $88.50  
  Purchase #4 $155.51   8.782%   $169.1669   $169.17   $169.15   $169.20  
  Purchase #5 $187.69   5.249%   $197.5418   $197.54   $197.55   $197.50  
  Purchase #6 $207.58   12.675%   $233.8908   $233.89   $233.90   $233.90  
  Purchase #7 $145.31   10.822%   $161.0354   $161.04   $161.05   $161.00  
  7 purchase totals = $1,007.27       $1,093.1688   $1,093.17   $1,093.20   $1,093.10