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 $208.46   13.694%   $237.0065   $237.01   $237.00   $237.00  
  Purchase #2 $58.65   7.370%   $62.9725   $62.97   $62.95   $63.00  
  Purchase #3 $133.64   11.328%   $148.7787   $148.78   $148.80   $148.80  
  Purchase #4 $175.99   3.868%   $182.7973   $182.80   $182.80   $182.80  
  Purchase #5 $167.99   7.206%   $180.0954   $180.10   $180.10   $180.10  
  Purchase #6 $127.94   12.570%   $144.0221   $144.02   $144.00   $144.00  
  Purchase #7 $110.77   7.401%   $118.9681   $118.97   $118.95   $119.00  
  7 purchase totals = $983.44       $1,074.6406   $1,074.65   $1,074.60   $1,074.70