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 $182.62   6.780%   $195.0016   $195.00   $195.00   $195.00  
  Purchase #2 $117.86   8.477%   $127.851   $127.85   $127.85   $127.90  
  Purchase #3 $117.71   10.292%   $129.8247   $129.82   $129.80   $129.80  
  Purchase #4 $137.32   3.103%   $141.581   $141.58   $141.60   $141.60  
  Purchase #5 $119.82   4.262%   $124.9267   $124.93   $124.95   $124.90  
  Purchase #6 $128.59   4.496%   $134.3714   $134.37   $134.35   $134.40  
  Purchase #7 $102.79   13.109%   $116.2647   $116.26   $116.25   $116.30  
  7 purchase totals = $906.71       $969.8211   $969.81   $969.80   $969.90