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 $56.85   9.110%   $62.029   $62.03   $62.05   $62.00  
  Purchase #2 $132.57   4.758%   $138.8777   $138.88   $138.90   $138.90  
  Purchase #3 $195.79   5.588%   $206.7307   $206.73   $206.75   $206.70  
  Purchase #4 $129.99   3.609%   $134.6813   $134.68   $134.70   $134.70  
  Purchase #5 $244.44   11.661%   $272.9441   $272.94   $272.95   $272.90  
  Purchase #6 $205.55   3.213%   $212.1543   $212.15   $212.15   $212.20  
  Purchase #7 $14.68   12.845%   $16.5656   $16.57   $16.55   $16.60  
  7 purchase totals = $979.87       $1,043.9827   $1,043.98   $1,044.05   $1,044.00