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	$14.49	11.293%	$16.1264	$16.13	$16.15	$16.10
Purchase #2	$11.50	12.448%	$12.9315	$12.93	$12.95	$12.90
Purchase #3	$116.82	11.429%	$130.1714	$130.17	$130.15	$130.20
Purchase #4	$38.91	4.243%	$40.561	$40.56	$40.55	$40.60
Purchase #5	$141.90	12.342%	$159.4133	$159.41	$159.40	$159.40
Purchase #6	$29.99	10.852%	$33.2445	$33.24	$33.25	$33.20
Purchase #7	$30.61	7.332%	$32.8543	$32.85	$32.85	$32.90
7 purchase totals =	$384.22		$425.3024	$425.29	$425.30	$425.30