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 $69.85   6.176%   $74.1639   $74.16   $74.15   $74.20  
  Purchase #2 $110.57   6.687%   $117.9638   $117.96   $117.95   $118.00  
  Purchase #3 $178.77   4.341%   $186.5304   $186.53   $186.55   $186.50  
  Purchase #4 $136.87   9.312%   $149.6153   $149.62   $149.60   $149.60  
  Purchase #5 $142.68   9.437%   $156.1447   $156.14   $156.15   $156.10  
  Purchase #6 $57.64   8.866%   $62.7504   $62.75   $62.75   $62.80  
  Purchase #7 $10.28   4.163%   $10.708   $10.71   $10.70   $10.70  
  7 purchase totals = $706.66       $757.8765   $757.87   $757.85   $757.90