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 $68.94   10.119%   $75.916   $75.92   $75.90   $75.90  
  Purchase #2 $214.80   8.729%   $233.5499   $233.55   $233.55   $233.50  
  Purchase #3 $248.42   5.555%   $262.2197   $262.22   $262.20   $262.20  
  Purchase #4 $166.32   11.682%   $185.7495   $185.75   $185.75   $185.70  
  Purchase #5 $181.62   8.801%   $197.6044   $197.60   $197.60   $197.60  
  Purchase #6 $232.50   5.129%   $244.4249   $244.42   $244.40   $244.40  
  Purchase #7 $138.37   13.206%   $156.6431   $156.64   $156.65   $156.60  
  7 purchase totals = $1,250.97       $1,356.1075   $1,356.10   $1,356.05   $1,355.90