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 $66.29   5.519%   $69.9485   $69.95   $69.95   $69.90  
  Purchase #2 $248.38   10.545%   $274.5717   $274.57   $274.55   $274.60  
  Purchase #3 $7.83   3.442%   $8.0995   $8.10   $8.10   $8.10  
  Purchase #4 $74.71   3.458%   $77.2935   $77.29   $77.30   $77.30  
  Purchase #5 $177.39   11.389%   $197.5929   $197.59   $197.60   $197.60  
  Purchase #6 $83.48   9.801%   $91.6619   $91.66   $91.65   $91.70  
  Purchase #7 $60.86   8.138%   $65.8128   $65.81   $65.80   $65.80  
  7 purchase totals = $718.94       $784.9808   $784.97   $784.95   $785.00