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 $68.67   10.158%   $75.6455   $75.65   $75.65   $75.60  
  Purchase #2 $85.58   13.566%   $97.1898   $97.19   $97.20   $97.20  
  Purchase #3 $66.76   8.469%   $72.4139   $72.41   $72.40   $72.40  
  Purchase #4 $174.73   10.725%   $193.4698   $193.47   $193.45   $193.50  
  Purchase #5 $223.50   3.861%   $232.1293   $232.13   $232.15   $232.10  
  Purchase #6 $207.86   12.675%   $234.2063   $234.21   $234.20   $234.20  
  Purchase #7 $195.61   9.277%   $213.7567   $213.76   $213.75   $213.80  
  7 purchase totals = $1,022.71       $1,118.8113   $1,118.82   $1,118.80   $1,118.80