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 $93.88   4.483%   $98.0886   $98.09   $98.10   $98.10  
  Purchase #2 $212.95   3.285%   $219.9454   $219.95   $219.95   $219.90  
  Purchase #3 $54.99   4.542%   $57.4876   $57.49   $57.50   $57.50  
  Purchase #4 $47.53   10.487%   $52.5145   $52.51   $52.50   $52.50  
  Purchase #5 $145.60   8.333%   $157.7328   $157.73   $157.75   $157.70  
  Purchase #6 $233.77   12.757%   $263.592   $263.59   $263.60   $263.60  
  Purchase #7 $241.93   5.530%   $255.3087   $255.31   $255.30   $255.30  
  7 purchase totals = $1,030.65       $1,104.6696   $1,104.67   $1,104.70   $1,104.60