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 $72.96   13.334%   $82.6885   $82.69   $82.70   $82.70  
  Purchase #2 $216.98   9.180%   $236.8988   $236.90   $236.90   $236.90  
  Purchase #3 $201.54   5.836%   $213.3019   $213.30   $213.30   $213.30  
  Purchase #4 $43.72   5.559%   $46.1504   $46.15   $46.15   $46.20  
  Purchase #5 $133.44   10.279%   $147.1563   $147.16   $147.15   $147.20  
  Purchase #6 $74.47   9.294%   $81.3912   $81.39   $81.40   $81.40  
  Purchase #7 $198.99   3.800%   $206.5516   $206.55   $206.55   $206.60  
  7 purchase totals = $942.10       $1,014.1387   $1,014.14   $1,014.15   $1,014.30