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 $210.70   10.404%   $232.6212   $232.62   $232.60   $232.60  
  Purchase #2 $165.93   9.832%   $182.2442   $182.24   $182.25   $182.20  
  Purchase #3 $101.82   11.305%   $113.3308   $113.33   $113.35   $113.30  
  Purchase #4 $207.58   5.667%   $219.3436   $219.34   $219.35   $219.30  
  Purchase #5 $86.92   6.636%   $92.688   $92.69   $92.70   $92.70  
  Purchase #6 $178.96   7.135%   $191.7288   $191.73   $191.75   $191.70  
  Purchase #7 $149.54   13.187%   $169.2598   $169.26   $169.25   $169.30  
  7 purchase totals = $1,101.45       $1,201.2164   $1,201.21   $1,201.25   $1,201.10