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 $85.82   12.545%   $96.5861   $96.59   $96.60   $96.60  
  Purchase #2 $113.59   5.260%   $119.5648   $119.56   $119.55   $119.60  
  Purchase #3 $193.26   5.267%   $203.439   $203.44   $203.45   $203.40  
  Purchase #4 $114.33   4.178%   $119.1067   $119.11   $119.10   $119.10  
  Purchase #5 $89.96   3.662%   $93.2543   $93.25   $93.25   $93.30  
  Purchase #6 $51.96   9.511%   $56.9019   $56.90   $56.90   $56.90  
  Purchase #7 $62.80   7.323%   $67.3988   $67.40   $67.40   $67.40  
  7 purchase totals = $711.72       $756.2516   $756.25   $756.25   $756.30