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 $119.33   5.242%   $125.5853   $125.59   $125.60   $125.60  
  Purchase #2 $106.57   7.509%   $114.5723   $114.57   $114.55   $114.60  
  Purchase #3 $35.37   11.625%   $39.4818   $39.48   $39.50   $39.50  
  Purchase #4 $152.42   9.667%   $167.1544   $167.15   $167.15   $167.20  
  Purchase #5 $134.39   5.467%   $141.7371   $141.74   $141.75   $141.70  
  Purchase #6 $215.78   4.113%   $224.655   $224.66   $224.65   $224.70  
  Purchase #7 $160.55   5.216%   $168.9243   $168.92   $168.90   $168.90  
  7 purchase totals = $924.41       $982.1102   $982.11   $982.10   $982.20