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 $85.69   13.181%   $96.9848   $96.98   $97.00   $97.00  
  Purchase #2 $218.97   12.277%   $245.8529   $245.85   $245.85   $245.90  
  Purchase #3 $76.58   11.804%   $85.6195   $85.62   $85.60   $85.60  
  Purchase #4 $124.62   6.272%   $132.4362   $132.44   $132.45   $132.40  
  Purchase #5 $161.74   12.709%   $182.2955   $182.30   $182.30   $182.30  
  Purchase #6 $23.90   9.705%   $26.2195   $26.22   $26.20   $26.20  
  Purchase #7 $228.38   12.184%   $256.2058   $256.21   $256.20   $256.20  
  7 purchase totals = $919.88       $1,025.6142   $1,025.62   $1,025.60   $1,025.60