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 $92.28   6.511%   $98.2884   $98.29   $98.30   $98.30  
  Purchase #2 $235.53   4.485%   $246.0935   $246.09   $246.10   $246.10  
  Purchase #3 $120.99   10.664%   $133.8924   $133.89   $133.90   $133.90  
  Purchase #4 $115.50   3.779%   $119.8647   $119.86   $119.85   $119.90  
  Purchase #5 $248.91   12.608%   $280.2926   $280.29   $280.30   $280.30  
  Purchase #6 $28.59   10.377%   $31.5568   $31.56   $31.55   $31.60  
  Purchase #7 $236.67   6.676%   $252.4701   $252.47   $252.45   $252.50  
  7 purchase totals = $1,078.47       $1,162.4585   $1,162.45   $1,162.45   $1,162.60