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 $224.36   9.732%   $246.1947   $246.19   $246.20   $246.20  
  Purchase #2 $66.47   13.738%   $75.6016   $75.60   $75.60   $75.60  
  Purchase #3 $173.57   12.590%   $195.4225   $195.42   $195.40   $195.40  
  Purchase #4 $170.30   9.412%   $186.3286   $186.33   $186.35   $186.30  
  Purchase #5 $94.57   3.210%   $97.6057   $97.61   $97.60   $97.60  
  Purchase #6 $242.98   13.237%   $275.1433   $275.14   $275.15   $275.10  
  Purchase #7 $72.28   6.102%   $76.6905   $76.69   $76.70   $76.70  
  7 purchase totals = $1,044.53       $1,152.9869   $1,152.98   $1,153.00   $1,152.90