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 $66.38   5.223%   $69.847   $69.85   $69.85   $69.80  
  Purchase #2 $35.41   5.252%   $37.2697   $37.27   $37.25   $37.30  
  Purchase #3 $176.81   9.540%   $193.6777   $193.68   $193.70   $193.70  
  Purchase #4 $117.99   6.677%   $125.8682   $125.87   $125.85   $125.90  
  Purchase #5 $218.80   5.482%   $230.7946   $230.79   $230.80   $230.80  
  Purchase #6 $52.87   6.860%   $56.4969   $56.50   $56.50   $56.50  
  Purchase #7 $20.85   11.241%   $23.1937   $23.19   $23.20   $23.20  
  7 purchase totals = $689.11       $737.1478   $737.15   $737.15   $737.20