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 $86.55   10.559%   $95.6888   $95.69   $95.70   $95.70  
  Purchase #2 $115.36   6.631%   $123.0095   $123.01   $123.00   $123.00  
  Purchase #3 $192.88   13.588%   $219.0885   $219.09   $219.10   $219.10  
  Purchase #4 $21.51   7.368%   $23.0949   $23.09   $23.10   $23.10  
  Purchase #5 $236.51   5.459%   $249.4211   $249.42   $249.40   $249.40  
  Purchase #6 $238.72   11.514%   $266.2062   $266.21   $266.20   $266.20  
  Purchase #7 $219.78   13.111%   $248.5954   $248.60   $248.60   $248.60  
  7 purchase totals = $1,111.31       $1,225.1044   $1,225.11   $1,225.10   $1,225.10