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 $86.63   11.595%   $96.6747   $96.67   $96.65   $96.70  
  Purchase #2 $156.68   11.446%   $174.6136   $174.61   $174.60   $174.60  
  Purchase #3 $153.70   8.615%   $166.9413   $166.94   $166.95   $166.90  
  Purchase #4 $169.53   4.371%   $176.9402   $176.94   $176.95   $176.90  
  Purchase #5 $88.66   7.396%   $95.2173   $95.22   $95.20   $95.20  
  Purchase #6 $42.26   7.153%   $45.2829   $45.28   $45.30   $45.30  
  Purchase #7 $6.50   3.240%   $6.7106   $6.71   $6.70   $6.70  
  7 purchase totals = $703.96       $762.3806   $762.37   $762.35   $762.30