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 $59.25   4.248%   $61.7669   $61.77   $61.75   $61.80  
  Purchase #2 $70.99   6.392%   $75.5277   $75.53   $75.55   $75.50  
  Purchase #3 $35.30   8.261%   $38.2161   $38.22   $38.20   $38.20  
  Purchase #4 $49.61   7.677%   $53.4186   $53.42   $53.40   $53.40  
  Purchase #5 $212.90   5.763%   $225.1694   $225.17   $225.15   $225.20  
  Purchase #6 $196.93   13.676%   $223.8621   $223.86   $223.85   $223.90  
  Purchase #7 $62.59   8.848%   $68.128   $68.13   $68.15   $68.10  
  7 purchase totals = $687.57       $746.0888   $746.10   $746.05   $746.10