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 $224.25   7.530%   $241.136   $241.14   $241.15   $241.10  
  Purchase #2 $75.66   10.179%   $83.3614   $83.36   $83.35   $83.40  
  Purchase #3 $26.58   8.162%   $28.7495   $28.75   $28.75   $28.70  
  Purchase #4 $150.82   7.702%   $162.4362   $162.44   $162.45   $162.40  
  Purchase #5 $109.56   6.707%   $116.9082   $116.91   $116.90   $116.90  
  Purchase #6 $217.87   4.479%   $227.6284   $227.63   $227.65   $227.60  
  Purchase #7 $190.59   7.841%   $205.5342   $205.53   $205.55   $205.50  
  7 purchase totals = $995.33       $1,065.7539   $1,065.76   $1,065.80   $1,065.60