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   6.862%   $73.6707   $73.67   $73.65   $73.70  
  Purchase #2 $217.38   7.302%   $233.2531   $233.25   $233.25   $233.30  
  Purchase #3 $214.44   13.758%   $243.9427   $243.94   $243.95   $243.90  
  Purchase #4 $196.96   3.828%   $204.4996   $204.50   $204.50   $204.50  
  Purchase #5 $8.34   3.275%   $8.6131   $8.61   $8.60   $8.60  
  Purchase #6 $214.43   12.541%   $241.3217   $241.32   $241.30   $241.30  
  Purchase #7 $181.81   7.396%   $195.2567   $195.26   $195.25   $195.30  
  7 purchase totals = $1,102.30       $1,200.5576   $1,200.55   $1,200.50   $1,200.60