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 $56.92   5.167%   $59.8611   $59.86   $59.85   $59.90  
  Purchase #2 $244.70   8.816%   $266.2728   $266.27   $266.25   $266.30  
  Purchase #3 $234.68   10.323%   $258.906   $258.91   $258.90   $258.90  
  Purchase #4 $186.64   11.538%   $208.1745   $208.17   $208.15   $208.20  
  Purchase #5 $34.63   6.348%   $36.8283   $36.83   $36.85   $36.80  
  Purchase #6 $168.33   8.118%   $181.995   $182.00   $182.00   $182.00  
  Purchase #7 $213.78   4.317%   $223.0089   $223.01   $223.00   $223.00  
  7 purchase totals = $1,139.68       $1,235.0466   $1,235.05   $1,235.00   $1,235.10