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 $125.68   5.585%   $132.6992   $132.70   $132.70   $132.70  
  Purchase #2 $92.99   6.218%   $98.7721   $98.77   $98.75   $98.80  
  Purchase #3 $92.62   7.408%   $99.4813   $99.48   $99.50   $99.50  
  Purchase #4 $67.43   12.791%   $76.055   $76.06   $76.05   $76.10  
  Purchase #5 $178.94   5.604%   $188.9678   $188.97   $188.95   $189.00  
  Purchase #6 $199.49   6.839%   $213.1331   $213.13   $213.15   $213.10  
  Purchase #7 $215.76   8.585%   $234.283   $234.28   $234.30   $234.30  
  7 purchase totals = $972.91       $1,043.3915   $1,043.39   $1,043.40   $1,043.50