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 $59.42   5.528%   $62.7047   $62.70   $62.70   $62.70  
  Purchase #2 $111.46   6.208%   $118.3794   $118.38   $118.40   $118.40  
  Purchase #3 $5.48   9.733%   $6.0134   $6.01   $6.00   $6.00  
  Purchase #4 $171.82   4.223%   $179.076   $179.08   $179.10   $179.10  
  Purchase #5 $185.70   5.354%   $195.6424   $195.64   $195.65   $195.60  
  Purchase #6 $198.97   8.564%   $216.0098   $216.01   $216.00   $216.00  
  Purchase #7 $161.35   13.856%   $183.7067   $183.71   $183.70   $183.70  
  7 purchase totals = $894.20       $961.5324   $961.53   $961.55   $961.50