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 $37.82   9.343%   $41.3535   $41.35   $41.35   $41.40  
  Purchase #2 $248.98   10.596%   $275.3619   $275.36   $275.35   $275.40  
  Purchase #3 $53.33   8.850%   $58.0497   $58.05   $58.05   $58.00  
  Purchase #4 $240.53   3.870%   $249.8385   $249.84   $249.85   $249.80  
  Purchase #5 $192.55   11.213%   $214.1406   $214.14   $214.15   $214.10  
  Purchase #6 $106.27   12.110%   $119.1393   $119.14   $119.15   $119.10  
  Purchase #7 $153.73   5.416%   $162.056   $162.06   $162.05   $162.10  
  7 purchase totals = $1,033.21       $1,119.9395   $1,119.94   $1,119.95   $1,119.90