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 $38.66   7.691%   $41.6333   $41.63   $41.65   $41.60  
  Purchase #2 $246.73   11.614%   $275.3852   $275.39   $275.40   $275.40  
  Purchase #3 $59.26   7.534%   $63.7246   $63.72   $63.70   $63.70  
  Purchase #4 $102.55   3.232%   $105.8644   $105.86   $105.85   $105.90  
  Purchase #5 $157.91   11.643%   $176.2955   $176.30   $176.30   $176.30  
  Purchase #6 $138.92   9.136%   $151.6117   $151.61   $151.60   $151.60  
  Purchase #7 $123.58   13.306%   $140.0236   $140.02   $140.00   $140.00  
  7 purchase totals = $867.61       $954.5383   $954.53   $954.50   $954.50