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	$118.36	10.327%	$130.583	$130.58	$130.60	$130.60
Purchase #2	$116.81	12.782%	$131.7407	$131.74	$131.75	$131.70
Purchase #3	$13.93	5.599%	$14.7099	$14.71	$14.70	$14.70
Purchase #4	$141.72	13.305%	$160.5758	$160.58	$160.60	$160.60
Purchase #5	$87.39	13.739%	$99.3965	$99.40	$99.40	$99.40
Purchase #6	$162.31	5.523%	$171.2744	$171.27	$171.25	$171.30
Purchase #7	$32.86	4.272%	$34.2638	$34.26	$34.25	$34.30
7 purchase totals =	$673.38		$742.5441	$742.54	$742.55	$742.60