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 $88.70   4.564%   $92.7483   $92.75   $92.75   $92.70  
  Purchase #2 $175.43   11.410%   $195.4466   $195.45   $195.45   $195.40  
  Purchase #3 $248.31   11.369%   $276.5404   $276.54   $276.55   $276.50  
  Purchase #4 $89.41   11.773%   $99.9362   $99.94   $99.95   $99.90  
  Purchase #5 $20.85   10.400%   $23.0184   $23.02   $23.00   $23.00  
  Purchase #6 $244.57   10.863%   $271.1376   $271.14   $271.15   $271.10  
  Purchase #7 $219.79   7.620%   $236.538   $236.54   $236.55   $236.50  
  7 purchase totals = $1,087.06       $1,195.3655   $1,195.38   $1,195.40   $1,195.10