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 $69.63   9.208%   $76.0415   $76.04   $76.05   $76.00  
  Purchase #2 $107.97   13.296%   $122.3257   $122.33   $122.35   $122.30  
  Purchase #3 $188.73   4.417%   $197.0662   $197.07   $197.05   $197.10  
  Purchase #4 $238.41   5.871%   $252.4071   $252.41   $252.40   $252.40  
  Purchase #5 $199.35   8.664%   $216.6217   $216.62   $216.60   $216.60  
  Purchase #6 $91.39   12.840%   $103.1245   $103.12   $103.10   $103.10  
  Purchase #7 $41.47   12.700%   $46.7367   $46.74   $46.75   $46.70  
  7 purchase totals = $936.95       $1,014.3234   $1,014.33   $1,014.30   $1,014.20