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	$161.47	7.256%	$173.1863	$173.19	$173.20	$173.20
Purchase #2	$237.74	3.305%	$245.5973	$245.60	$245.60	$245.60
Purchase #3	$142.60	13.153%	$161.3562	$161.36	$161.35	$161.40
Purchase #4	$89.95	12.160%	$100.8879	$100.89	$100.90	$100.90
Purchase #5	$43.39	4.514%	$45.3486	$45.35	$45.35	$45.30
Purchase #6	$235.70	7.571%	$253.5448	$253.54	$253.55	$253.50
Purchase #7	$60.69	8.232%	$65.686	$65.69	$65.70	$65.70
7 purchase totals =	$971.54		$1,045.6071	$1,045.62	$1,045.65	$1,045.60