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 $56.48   10.232%   $62.259   $62.26   $62.25   $62.30  
  Purchase #2 $63.46   5.571%   $66.9954   $67.00   $67.00   $67.00  
  Purchase #3 $177.74   4.618%   $185.948   $185.95   $185.95   $185.90  
  Purchase #4 $83.99   11.670%   $93.7916   $93.79   $93.80   $93.80  
  Purchase #5 $111.63   5.140%   $117.3678   $117.37   $117.35   $117.40  
  Purchase #6 $86.30   8.212%   $93.387   $93.39   $93.40   $93.40  
  Purchase #7 $220.97   9.507%   $241.9776   $241.98   $242.00   $242.00  
  7 purchase totals = $800.57       $861.7264   $861.74   $861.75   $861.80