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 $43.40   9.740%   $47.6272   $47.63   $47.65   $47.60  
  Purchase #2 $236.53   4.784%   $247.8456   $247.85   $247.85   $247.80  
  Purchase #3 $196.90   8.779%   $214.1859   $214.19   $214.20   $214.20  
  Purchase #4 $154.97   10.537%   $171.2992   $171.30   $171.30   $171.30  
  Purchase #5 $236.99   10.725%   $262.4072   $262.41   $262.40   $262.40  
  Purchase #6 $67.71   10.769%   $75.0017   $75.00   $75.00   $75.00  
  Purchase #7 $167.69   3.789%   $174.0438   $174.04   $174.05   $174.00  
  7 purchase totals = $1,104.19       $1,192.4106   $1,192.42   $1,192.45   $1,192.30