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 $126.42   5.874%   $133.8459   $133.85   $133.85   $133.80  
  Purchase #2 $170.54   4.327%   $177.9193   $177.92   $177.90   $177.90  
  Purchase #3 $46.99   13.113%   $53.1518   $53.15   $53.15   $53.20  
  Purchase #4 $159.61   3.556%   $165.2857   $165.29   $165.30   $165.30  
  Purchase #5 $22.73   5.675%   $24.0199   $24.02   $24.00   $24.00  
  Purchase #6 $176.72   13.404%   $200.4075   $200.41   $200.40   $200.40  
  Purchase #7 $8.81   13.770%   $10.0231   $10.02   $10.00   $10.00  
  7 purchase totals = $711.82       $764.6532   $764.66   $764.60   $764.60