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 $84.33   12.640%   $94.9893   $94.99   $95.00   $95.00  
  Purchase #2 $206.69   10.321%   $228.0225   $228.02   $228.00   $228.00  
  Purchase #3 $202.35   9.719%   $222.0164   $222.02   $222.00   $222.00  
  Purchase #4 $86.79   9.315%   $94.8745   $94.87   $94.85   $94.90  
  Purchase #5 $72.67   13.869%   $82.7486   $82.75   $82.75   $82.70  
  Purchase #6 $101.47   9.648%   $111.2598   $111.26   $111.25   $111.30  
  Purchase #7 $218.40   11.110%   $242.6642   $242.66   $242.65   $242.70  
  7 purchase totals = $972.70       $1,076.5753   $1,076.57   $1,076.50   $1,076.60