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	$98.33	9.787%	$107.9536	$107.95	$107.95	$108.00
Purchase #2	$235.87	8.166%	$255.1311	$255.13	$255.15	$255.10
Purchase #3	$208.93	11.783%	$233.5482	$233.55	$233.55	$233.50
Purchase #4	$230.64	10.584%	$255.0509	$255.05	$255.05	$255.10
Purchase #5	$73.46	5.215%	$77.2909	$77.29	$77.30	$77.30
Purchase #6	$245.72	4.864%	$257.6718	$257.67	$257.65	$257.70
Purchase #7	$138.89	5.635%	$146.7165	$146.72	$146.70	$146.70
7 purchase totals =	$1,231.84		$1,333.3630	$1,333.36	$1,333.35	$1,333.40