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	$72.83	4.604%	$76.1831	$76.18	$76.20	$76.20
Purchase #2	$13.66	12.362%	$15.3486	$15.35	$15.35	$15.30
Purchase #3	$13.88	5.255%	$14.6094	$14.61	$14.60	$14.60
Purchase #4	$23.25	4.176%	$24.2209	$24.22	$24.20	$24.20
Purchase #5	$81.78	10.625%	$90.4691	$90.47	$90.45	$90.50
Purchase #6	$14.34	4.768%	$15.0237	$15.02	$15.00	$15.00
Purchase #7	$36.54	3.659%	$37.877	$37.88	$37.90	$37.90
7 purchase totals =	$256.28		$273.7318	$273.73	$273.70	$273.70