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 $212.72   13.433%   $241.2947   $241.29   $241.30   $241.30  
  Purchase #2 $17.53   9.509%   $19.1969   $19.20   $19.20   $19.20  
  Purchase #3 $36.36   4.516%   $38.002   $38.00   $38.00   $38.00  
  Purchase #4 $61.53   4.677%   $64.4078   $64.41   $64.40   $64.40  
  Purchase #5 $108.65   5.149%   $114.2444   $114.24   $114.25   $114.20  
  Purchase #6 $125.98   4.661%   $131.8519   $131.85   $131.85   $131.90  
  Purchase #7 $111.41   10.201%   $122.7749   $122.77   $122.75   $122.80  
  7 purchase totals = $674.18       $731.7726   $731.76   $731.75   $731.80