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 $107.84   6.261%   $114.5919   $114.59   $114.60   $114.60  
  Purchase #2 $48.39   7.317%   $51.9307   $51.93   $51.95   $51.90  
  Purchase #3 $154.59   12.559%   $174.005   $174.01   $174.00   $174.00  
  Purchase #4 $193.48   3.352%   $199.9654   $199.97   $199.95   $200.00  
  Purchase #5 $69.88   6.323%   $74.2985   $74.30   $74.30   $74.30  
  Purchase #6 $206.51   7.379%   $221.7484   $221.75   $221.75   $221.70  
  Purchase #7 $104.40   11.764%   $116.6816   $116.68   $116.70   $116.70  
  7 purchase totals = $885.09       $953.2215   $953.23   $953.25   $953.20