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 $196.51   9.657%   $215.487   $215.49   $215.50   $215.50  
  Purchase #2 $142.26   7.865%   $153.4487   $153.45   $153.45   $153.40  
  Purchase #3 $66.97   4.719%   $70.1303   $70.13   $70.15   $70.10  
  Purchase #4 $185.40   5.251%   $195.1354   $195.14   $195.15   $195.10  
  Purchase #5 $166.31   3.826%   $172.673   $172.67   $172.65   $172.70  
  Purchase #6 $139.63   4.834%   $146.3797   $146.38   $146.40   $146.40  
  Purchase #7 $75.34   11.221%   $83.7939   $83.79   $83.80   $83.80  
  7 purchase totals = $972.42       $1,037.0480   $1,037.05   $1,037.10   $1,037.00