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 $32.91   10.139%   $36.2467   $36.25   $36.25   $36.20  
  Purchase #2 $102.50   3.667%   $106.2587   $106.26   $106.25   $106.30  
  Purchase #3 $227.50   7.305%   $244.1189   $244.12   $244.10   $244.10  
  Purchase #4 $114.83   3.449%   $118.7905   $118.79   $118.80   $118.80  
  Purchase #5 $199.85   3.178%   $206.2012   $206.20   $206.20   $206.20  
  Purchase #6 $146.90   4.340%   $153.2755   $153.28   $153.30   $153.30  
  Purchase #7 $229.26   3.541%   $237.3781   $237.38   $237.40   $237.40  
  7 purchase totals = $1,053.75       $1,102.2696   $1,102.28   $1,102.30   $1,102.30