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 $76.79   7.206%   $82.3235   $82.32   $82.30   $82.30  
  Purchase #2 $195.26   9.338%   $213.4934   $213.49   $213.50   $213.50  
  Purchase #3 $211.25   7.254%   $226.5741   $226.57   $226.55   $226.60  
  Purchase #4 $136.74   10.792%   $151.497   $151.50   $151.50   $151.50  
  Purchase #5 $230.44   7.193%   $247.0155   $247.02   $247.00   $247.00  
  Purchase #6 $118.30   12.791%   $133.4318   $133.43   $133.45   $133.40  
  Purchase #7 $98.39   9.635%   $107.8699   $107.87   $107.85   $107.90  
  7 purchase totals = $1,067.17       $1,162.2052   $1,162.20   $1,162.15   $1,162.20