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	$191.62	7.110%	$205.2442	$205.24	$205.25	$205.20
Purchase #2	$49.69	3.109%	$51.2349	$51.23	$51.25	$51.20
Purchase #3	$246.52	3.175%	$254.347	$254.35	$254.35	$254.30
Purchase #4	$248.29	12.536%	$279.4156	$279.42	$279.40	$279.40
Purchase #5	$63.64	4.195%	$66.3097	$66.31	$66.30	$66.30
Purchase #6	$188.48	10.606%	$208.4702	$208.47	$208.45	$208.50
Purchase #7	$142.45	10.640%	$157.6067	$157.61	$157.60	$157.60
7 purchase totals =	$1,130.69		$1,222.6283	$1,222.63	$1,222.60	$1,222.50