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 $224.89   7.225%   $241.1383   $241.14   $241.15   $241.10  
  Purchase #2 $150.47   10.282%   $165.9413   $165.94   $165.95   $165.90  
  Purchase #3 $145.82   8.317%   $157.9478   $157.95   $157.95   $157.90  
  Purchase #4 $79.67   7.354%   $85.5289   $85.53   $85.55   $85.50  
  Purchase #5 $215.71   8.428%   $233.89   $233.89   $233.90   $233.90  
  Purchase #6 $214.70   5.690%   $226.9164   $226.92   $226.90   $226.90  
  Purchase #7 $17.87   7.554%   $19.2199   $19.22   $19.20   $19.20  
  7 purchase totals = $1,049.13       $1,130.5826   $1,130.59   $1,130.60   $1,130.40