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 $61.88   3.420%   $63.9963   $64.00   $64.00   $64.00  
  Purchase #2 $187.69   8.763%   $204.1373   $204.14   $204.15   $204.10  
  Purchase #3 $193.37   9.491%   $211.7227   $211.72   $211.70   $211.70  
  Purchase #4 $163.79   7.136%   $175.4781   $175.48   $175.50   $175.50  
  Purchase #5 $160.77   13.291%   $182.1379   $182.14   $182.15   $182.10  
  Purchase #6 $192.30   12.308%   $215.9683   $215.97   $215.95   $216.00  
  Purchase #7 $199.98   3.331%   $206.6413   $206.64   $206.65   $206.60  
  7 purchase totals = $1,159.78       $1,260.0819   $1,260.09   $1,260.10   $1,260.00