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	$143.33	13.123%	$162.1392	$162.14	$162.15	$162.10
Purchase #2	$47.72	3.743%	$49.5062	$49.51	$49.50	$49.50
Purchase #3	$10.93	12.804%	$12.3295	$12.33	$12.35	$12.30
Purchase #4	$83.42	12.698%	$94.0127	$94.01	$94.00	$94.00
Purchase #5	$137.46	13.186%	$155.5855	$155.59	$155.60	$155.60
Purchase #6	$52.33	12.496%	$58.8692	$58.87	$58.85	$58.90
Purchase #7	$34.26	8.848%	$37.2913	$37.29	$37.30	$37.30
7 purchase totals =	$509.45		$569.7336	$569.74	$569.75	$569.70