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 $39.32   5.549%   $41.5019   $41.50   $41.50   $41.50  
  Purchase #2 $107.62   9.323%   $117.6534   $117.65   $117.65   $117.70  
  Purchase #3 $197.60   10.704%   $218.7511   $218.75   $218.75   $218.80  
  Purchase #4 $81.34   12.577%   $91.5701   $91.57   $91.55   $91.60  
  Purchase #5 $216.27   9.304%   $236.3918   $236.39   $236.40   $236.40  
  Purchase #6 $23.43   4.492%   $24.4825   $24.48   $24.50   $24.50  
  Purchase #7 $29.63   6.426%   $31.534   $31.53   $31.55   $31.50  
  7 purchase totals = $695.21       $761.8848   $761.87   $761.90   $762.00