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 $58.97   6.244%   $62.6521   $62.65   $62.65   $62.70  
  Purchase #2 $119.26   5.456%   $125.7668   $125.77   $125.75   $125.80  
  Purchase #3 $229.72   5.643%   $242.6831   $242.68   $242.70   $242.70  
  Purchase #4 $39.82   4.514%   $41.6175   $41.62   $41.60   $41.60  
  Purchase #5 $227.62   13.316%   $257.9299   $257.93   $257.95   $257.90  
  Purchase #6 $227.82   4.190%   $237.3657   $237.37   $237.35   $237.40  
  Purchase #7 $190.27   12.649%   $214.3373   $214.34   $214.35   $214.30  
  7 purchase totals = $1,093.48       $1,182.3524   $1,182.36   $1,182.35   $1,182.40