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 $116.51   7.777%   $125.571   $125.57   $125.55   $125.60  
  Purchase #2 $250.26   6.363%   $266.184   $266.18   $266.20   $266.20  
  Purchase #3 $231.98   3.588%   $240.3034   $240.30   $240.30   $240.30  
  Purchase #4 $63.42   4.859%   $66.5016   $66.50   $66.50   $66.50  
  Purchase #5 $101.86   8.239%   $110.2522   $110.25   $110.25   $110.30  
  Purchase #6 $129.84   7.431%   $139.4884   $139.49   $139.50   $139.50  
  Purchase #7 $153.49   3.611%   $159.0325   $159.03   $159.05   $159.00  
  7 purchase totals = $1,047.36       $1,107.3331   $1,107.32   $1,107.35   $1,107.40