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 $214.25   6.243%   $227.6256   $227.63   $227.65   $227.60  
  Purchase #2 $12.44   13.545%   $14.125   $14.13   $14.15   $14.10  
  Purchase #3 $195.97   9.608%   $214.7988   $214.80   $214.80   $214.80  
  Purchase #4 $78.47   12.403%   $88.2026   $88.20   $88.20   $88.20  
  Purchase #5 $53.70   6.153%   $57.0042   $57.00   $57.00   $57.00  
  Purchase #6 $62.30   5.536%   $65.7489   $65.75   $65.75   $65.70  
  Purchase #7 $54.77   5.120%   $57.5742   $57.57   $57.55   $57.60  
  7 purchase totals = $671.90       $725.0793   $725.08   $725.10   $725.00