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 $236.92   4.359%   $247.2473   $247.25   $247.25   $247.20  
  Purchase #2 $111.65   7.147%   $119.6296   $119.63   $119.65   $119.60  
  Purchase #3 $131.38   7.467%   $141.1901   $141.19   $141.20   $141.20  
  Purchase #4 $145.85   7.241%   $156.411   $156.41   $156.40   $156.40  
  Purchase #5 $44.50   5.760%   $47.0632   $47.06   $47.05   $47.10  
  Purchase #6 $195.87   11.643%   $218.6751   $218.68   $218.70   $218.70  
  Purchase #7 $157.31   11.174%   $174.8878   $174.89   $174.90   $174.90  
  7 purchase totals = $1,023.48       $1,105.1041   $1,105.11   $1,105.15   $1,105.10