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 $208.51   4.394%   $217.6719   $217.67   $217.65   $217.70  
  Purchase #2 $195.37   8.838%   $212.6368   $212.64   $212.65   $212.60  
  Purchase #3 $59.87   10.835%   $66.3569   $66.36   $66.35   $66.40  
  Purchase #4 $230.28   3.864%   $239.178   $239.18   $239.20   $239.20  
  Purchase #5 $187.83   4.836%   $196.9135   $196.91   $196.90   $196.90  
  Purchase #6 $141.31   8.713%   $153.6223   $153.62   $153.60   $153.60  
  Purchase #7 $106.61   9.733%   $116.9864   $116.99   $117.00   $117.00  
  7 purchase totals = $1,129.78       $1,203.3658   $1,203.37   $1,203.35   $1,203.40