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 $59.26   3.274%   $61.2002   $61.20   $61.20   $61.20  
  Purchase #2 $211.91   8.423%   $229.7592   $229.76   $229.75   $229.80  
  Purchase #3 $191.37   11.646%   $213.657   $213.66   $213.65   $213.70  
  Purchase #4 $232.63   5.744%   $245.9923   $245.99   $246.00   $246.00  
  Purchase #5 $234.76   13.508%   $266.4714   $266.47   $266.45   $266.50  
  Purchase #6 $124.77   9.626%   $136.7804   $136.78   $136.80   $136.80  
  Purchase #7 $96.35   13.311%   $109.1751   $109.18   $109.20   $109.20  
  7 purchase totals = $1,151.05       $1,263.0356   $1,263.04   $1,263.05   $1,263.20