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 $141.29   8.782%   $153.6981   $153.70   $153.70   $153.70  
  Purchase #2 $236.56   12.408%   $265.9124   $265.91   $265.90   $265.90  
  Purchase #3 $182.96   13.175%   $207.065   $207.07   $207.05   $207.10  
  Purchase #4 $58.92   12.502%   $66.2862   $66.29   $66.30   $66.30  
  Purchase #5 $133.99   5.617%   $141.5162   $141.52   $141.50   $141.50  
  Purchase #6 $48.63   8.398%   $52.7139   $52.71   $52.70   $52.70  
  Purchase #7 $155.35   4.296%   $162.0238   $162.02   $162.00   $162.00  
  7 purchase totals = $957.70       $1,049.2156   $1,049.22   $1,049.15   $1,049.20