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 $72.82   4.783%   $76.303   $76.30   $76.30   $76.30  
  Purchase #2 $200.54   8.149%   $216.882   $216.88   $216.90   $216.90  
  Purchase #3 $188.79   12.844%   $213.0382   $213.04   $213.05   $213.00  
  Purchase #4 $241.43   6.549%   $257.2413   $257.24   $257.25   $257.20  
  Purchase #5 $197.46   6.259%   $209.819   $209.82   $209.80   $209.80  
  Purchase #6 $186.53   8.440%   $202.2731   $202.27   $202.25   $202.30  
  Purchase #7 $211.60   7.315%   $227.0785   $227.08   $227.10   $227.10  
  7 purchase totals = $1,299.17       $1,402.6351   $1,402.63   $1,402.65   $1,402.60