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 $206.93   8.862%   $225.2681   $225.27   $225.25   $225.30  
  Purchase #2 $202.71   5.852%   $214.5726   $214.57   $214.55   $214.60  
  Purchase #3 $236.97   6.738%   $252.937   $252.94   $252.95   $252.90  
  Purchase #4 $88.32   5.616%   $93.2801   $93.28   $93.30   $93.30  
  Purchase #5 $12.99   7.785%   $14.0013   $14.00   $14.00   $14.00  
  Purchase #6 $158.46   9.455%   $173.4424   $173.44   $173.45   $173.40  
  Purchase #7 $136.28   4.619%   $142.5748   $142.57   $142.55   $142.60  
  7 purchase totals = $1,042.66       $1,116.0763   $1,116.07   $1,116.05   $1,116.10