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 $207.82   3.792%   $215.7005   $215.70   $215.70   $215.70  
  Purchase #2 $210.74   7.399%   $226.3327   $226.33   $226.35   $226.30  
  Purchase #3 $59.75   4.330%   $62.3372   $62.34   $62.35   $62.30  
  Purchase #4 $101.39   5.598%   $107.0658   $107.07   $107.05   $107.10  
  Purchase #5 $71.33   6.737%   $76.1355   $76.14   $76.15   $76.10  
  Purchase #6 $183.42   8.393%   $198.8144   $198.81   $198.80   $198.80  
  Purchase #7 $17.53   7.510%   $18.8465   $18.85   $18.85   $18.80  
  7 purchase totals = $851.98       $905.2326   $905.24   $905.25   $905.10