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 $124.76   13.319%   $141.3768   $141.38   $141.40   $141.40  
  Purchase #2 $215.95   12.727%   $243.434   $243.43   $243.45   $243.40  
  Purchase #3 $169.48   3.794%   $175.9101   $175.91   $175.90   $175.90  
  Purchase #4 $152.88   6.156%   $162.2913   $162.29   $162.30   $162.30  
  Purchase #5 $213.79   11.159%   $237.6468   $237.65   $237.65   $237.60  
  Purchase #6 $250.92   4.853%   $263.0971   $263.10   $263.10   $263.10  
  Purchase #7 $130.34   8.158%   $140.9731   $140.97   $140.95   $141.00  
  7 purchase totals = $1,258.12       $1,364.7292   $1,364.73   $1,364.75   $1,364.70