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 $83.35   13.411%   $94.5281   $94.53   $94.55   $94.50  
  Purchase #2 $214.85   4.264%   $224.0112   $224.01   $224.00   $224.00  
  Purchase #3 $106.80   12.733%   $120.3988   $120.40   $120.40   $120.40  
  Purchase #4 $169.42   9.300%   $185.1761   $185.18   $185.20   $185.20  
  Purchase #5 $206.42   10.651%   $228.4058   $228.41   $228.40   $228.40  
  Purchase #6 $233.29   10.272%   $257.2535   $257.25   $257.25   $257.30  
  Purchase #7 $139.83   12.511%   $157.3241   $157.32   $157.30   $157.30  
  7 purchase totals = $1,153.96       $1,267.0976   $1,267.10   $1,267.10   $1,267.10