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 $225.49   3.363%   $233.0732   $233.07   $233.05   $233.10  
  Purchase #2 $76.32   5.487%   $80.5077   $80.51   $80.50   $80.50  
  Purchase #3 $103.73   4.673%   $108.5773   $108.58   $108.60   $108.60  
  Purchase #4 $91.46   9.575%   $100.2173   $100.22   $100.20   $100.20  
  Purchase #5 $43.68   5.289%   $45.9902   $45.99   $46.00   $46.00  
  Purchase #6 $207.98   7.817%   $224.2378   $224.24   $224.25   $224.20  
  Purchase #7 $219.33   5.511%   $231.4173   $231.42   $231.40   $231.40  
  7 purchase totals = $967.99       $1,024.0208   $1,024.03   $1,024.00   $1,024.00