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 $214.91   13.742%   $244.4429   $244.44   $244.45   $244.40  
  Purchase #2 $61.34   11.377%   $68.3187   $68.32   $68.30   $68.30  
  Purchase #3 $145.32   5.766%   $153.6992   $153.70   $153.70   $153.70  
  Purchase #4 $74.29   6.826%   $79.361   $79.36   $79.35   $79.40  
  Purchase #5 $9.53   4.202%   $9.9305   $9.93   $9.95   $9.90  
  Purchase #6 $192.45   11.327%   $214.2488   $214.25   $214.25   $214.20  
  Purchase #7 $120.48   4.467%   $125.8618   $125.86   $125.85   $125.90  
  7 purchase totals = $818.32       $895.8629   $895.86   $895.85   $895.80