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 $152.55   8.541%   $165.5793   $165.58   $165.60   $165.60  
  Purchase #2 $232.56   12.805%   $262.3393   $262.34   $262.35   $262.30  
  Purchase #3 $68.75   10.771%   $76.1551   $76.16   $76.15   $76.20  
  Purchase #4 $65.74   6.162%   $69.7909   $69.79   $69.80   $69.80  
  Purchase #5 $169.60   7.548%   $182.4014   $182.40   $182.40   $182.40  
  Purchase #6 $153.42   7.707%   $165.2441   $165.24   $165.25   $165.20  
  Purchase #7 $135.62   11.163%   $150.7593   $150.76   $150.75   $150.80  
  7 purchase totals = $978.24       $1,072.2694   $1,072.27   $1,072.30   $1,072.30