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	$116.61	11.542%	$130.0691	$130.07	$130.05	$130.10
Purchase #2	$240.48	10.773%	$266.3869	$266.39	$266.40	$266.40
Purchase #3	$80.69	12.644%	$90.8924	$90.89	$90.90	$90.90
Purchase #4	$123.70	8.196%	$133.8385	$133.84	$133.85	$133.80
Purchase #5	$130.33	12.154%	$146.1703	$146.17	$146.15	$146.20
Purchase #6	$52.40	4.433%	$54.7229	$54.72	$54.70	$54.70
Purchase #7	$178.42	12.463%	$200.6565	$200.66	$200.65	$200.70
7 purchase totals =	$922.63		$1,022.7366	$1,022.74	$1,022.70	$1,022.80