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 $60.57   12.176%   $67.945   $67.95   $67.95   $67.90  
  Purchase #2 $230.58   9.830%   $253.246   $253.25   $253.25   $253.20  
  Purchase #3 $21.93   9.587%   $24.0324   $24.03   $24.05   $24.00  
  Purchase #4 $211.65   5.655%   $223.6188   $223.62   $223.60   $223.60  
  Purchase #5 $153.42   3.330%   $158.5289   $158.53   $158.55   $158.50  
  Purchase #6 $75.76   10.664%   $83.839   $83.84   $83.85   $83.80  
  Purchase #7 $130.64   8.669%   $141.9652   $141.97   $141.95   $142.00  
  7 purchase totals = $884.55       $953.1753   $953.19   $953.20   $953.00