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 $93.46   4.805%   $97.9508   $97.95   $97.95   $98.00  
  Purchase #2 $187.53   13.361%   $212.5859   $212.59   $212.60   $212.60  
  Purchase #3 $223.56   11.839%   $250.0273   $250.03   $250.05   $250.00  
  Purchase #4 $68.36   3.369%   $70.663   $70.66   $70.65   $70.70  
  Purchase #5 $178.44   9.113%   $194.7012   $194.70   $194.70   $194.70  
  Purchase #6 $183.89   6.425%   $195.7049   $195.70   $195.70   $195.70  
  Purchase #7 $208.25   12.487%   $234.2542   $234.25   $234.25   $234.30  
  7 purchase totals = $1,143.49       $1,255.8873   $1,255.88   $1,255.90   $1,256.00