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 $206.69   5.447%   $217.9484   $217.95   $217.95   $217.90  
  Purchase #2 $228.51   5.468%   $241.0049   $241.00   $241.00   $241.00  
  Purchase #3 $227.83   6.103%   $241.7345   $241.73   $241.75   $241.70  
  Purchase #4 $140.80   12.159%   $157.9199   $157.92   $157.90   $157.90  
  Purchase #5 $234.40   11.122%   $260.47   $260.47   $260.45   $260.50  
  Purchase #6 $91.74   8.126%   $99.1948   $99.19   $99.20   $99.20  
  Purchase #7 $222.86   6.492%   $237.3281   $237.33   $237.35   $237.30  
  7 purchase totals = $1,352.83       $1,455.6006   $1,455.59   $1,455.60   $1,455.50