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 $237.86   12.628%   $267.897   $267.90   $267.90   $267.90  
  Purchase #2 $8.29   13.397%   $9.4006   $9.40   $9.40   $9.40  
  Purchase #3 $210.63   4.568%   $220.2516   $220.25   $220.25   $220.30  
  Purchase #4 $193.50   5.571%   $204.2799   $204.28   $204.30   $204.30  
  Purchase #5 $234.93   4.212%   $244.8253   $244.83   $244.85   $244.80  
  Purchase #6 $190.46   12.761%   $214.7646   $214.76   $214.75   $214.80  
  Purchase #7 $69.89   5.293%   $73.5893   $73.59   $73.60   $73.60  
  7 purchase totals = $1,145.56       $1,235.0083   $1,235.01   $1,235.05   $1,235.10