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 $71.26   5.610%   $75.2577   $75.26   $75.25   $75.30  
  Purchase #2 $222.69   7.675%   $239.7815   $239.78   $239.80   $239.80  
  Purchase #3 $112.80   5.682%   $119.2093   $119.21   $119.20   $119.20  
  Purchase #4 $207.48   6.662%   $221.3023   $221.30   $221.30   $221.30  
  Purchase #5 $228.46   6.549%   $243.4218   $243.42   $243.40   $243.40  
  Purchase #6 $182.65   3.532%   $189.1012   $189.10   $189.10   $189.10  
  Purchase #7 $96.81   11.402%   $107.8483   $107.85   $107.85   $107.80  
  7 purchase totals = $1,122.15       $1,195.9221   $1,195.92   $1,195.90   $1,195.90