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 $215.82   7.124%   $231.195   $231.20   $231.20   $231.20  
  Purchase #2 $68.87   9.502%   $75.414   $75.41   $75.40   $75.40  
  Purchase #3 $113.78   3.160%   $117.3754   $117.38   $117.40   $117.40  
  Purchase #4 $12.76   6.751%   $13.6214   $13.62   $13.60   $13.60  
  Purchase #5 $201.56   11.427%   $224.5923   $224.59   $224.60   $224.60  
  Purchase #6 $233.79   12.708%   $263.5   $263.50   $263.50   $263.50  
  Purchase #7 $135.67   4.165%   $141.3207   $141.32   $141.30   $141.30  
  7 purchase totals = $982.25       $1,067.0188   $1,067.02   $1,067.00   $1,067.00