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 $109.97   8.211%   $118.9996   $119.00   $119.00   $119.00  
  Purchase #2 $62.95   4.549%   $65.8136   $65.81   $65.80   $65.80  
  Purchase #3 $22.47   7.151%   $24.0768   $24.08   $24.10   $24.10  
  Purchase #4 $224.57   9.452%   $245.7964   $245.80   $245.80   $245.80  
  Purchase #5 $106.86   3.439%   $110.5349   $110.53   $110.55   $110.50  
  Purchase #6 $81.98   4.661%   $85.8011   $85.80   $85.80   $85.80  
  Purchase #7 $82.77   11.441%   $92.2397   $92.24   $92.25   $92.20  
  7 purchase totals = $691.57       $743.2621   $743.26   $743.30   $743.20