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 $248.59   5.487%   $262.2301   $262.23   $262.25   $262.20  
  Purchase #2 $60.95   7.668%   $65.6236   $65.62   $65.60   $65.60  
  Purchase #3 $190.66   13.486%   $216.3724   $216.37   $216.35   $216.40  
  Purchase #4 $241.31   12.499%   $271.4713   $271.47   $271.45   $271.50  
  Purchase #5 $82.78   5.851%   $87.6235   $87.62   $87.60   $87.60  
  Purchase #6 $10.41   13.335%   $11.7982   $11.80   $11.80   $11.80  
  Purchase #7 $151.30   5.162%   $159.1101   $159.11   $159.10   $159.10  
  7 purchase totals = $986.00       $1,074.2292   $1,074.22   $1,074.15   $1,074.20