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 $68.35   6.414%   $72.734   $72.73   $72.75   $72.70  
  Purchase #2 $167.94   8.778%   $182.6818   $182.68   $182.70   $182.70  
  Purchase #3 $249.44   3.848%   $259.0385   $259.04   $259.05   $259.00  
  Purchase #4 $236.75   10.744%   $262.1864   $262.19   $262.20   $262.20  
  Purchase #5 $160.73   8.620%   $174.5849   $174.58   $174.60   $174.60  
  Purchase #6 $193.71   13.386%   $219.64   $219.64   $219.65   $219.60  
  Purchase #7 $206.55   7.430%   $221.8967   $221.90   $221.90   $221.90  
  7 purchase totals = $1,283.47       $1,392.7623   $1,392.76   $1,392.85   $1,392.70