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	$151.72	5.238%	$159.6671	$159.67	$159.65	$159.70
Purchase #2	$108.37	3.262%	$111.905	$111.91	$111.90	$111.90
Purchase #3	$172.77	8.662%	$187.7353	$187.74	$187.75	$187.70
Purchase #4	$224.51	11.508%	$250.3466	$250.35	$250.35	$250.30
Purchase #5	$172.32	4.206%	$179.5678	$179.57	$179.55	$179.60
Purchase #6	$47.67	8.492%	$51.7181	$51.72	$51.70	$51.70
Purchase #7	$72.87	5.831%	$77.119	$77.12	$77.10	$77.10
7 purchase totals =	$950.23		$1,018.0589	$1,018.08	$1,018.00	$1,018.00