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 $44.85   5.245%   $47.2024   $47.20   $47.20   $47.20  
  Purchase #2 $173.82   11.246%   $193.3678   $193.37   $193.35   $193.40  
  Purchase #3 $209.53   13.285%   $237.3661   $237.37   $237.35   $237.40  
  Purchase #4 $163.51   6.352%   $173.8962   $173.90   $173.90   $173.90  
  Purchase #5 $158.74   10.468%   $175.3569   $175.36   $175.35   $175.40  
  Purchase #6 $226.32   5.828%   $239.5099   $239.51   $239.50   $239.50  
  Purchase #7 $170.40   10.528%   $188.3397   $188.34   $188.35   $188.30  
  7 purchase totals = $1,147.17       $1,255.0390   $1,255.05   $1,255.00   $1,255.10