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	$187.45	13.439%	$212.6414	$212.64	$212.65	$212.60
Purchase #2	$144.99	10.109%	$159.647	$159.65	$159.65	$159.60
Purchase #3	$111.89	5.604%	$118.1603	$118.16	$118.15	$118.20
Purchase #4	$188.41	4.128%	$196.1876	$196.19	$196.20	$196.20
Purchase #5	$56.32	12.816%	$63.538	$63.54	$63.55	$63.50
Purchase #6	$128.81	4.243%	$134.2754	$134.28	$134.30	$134.30
Purchase #7	$181.52	5.452%	$191.4165	$191.42	$191.40	$191.40
7 purchase totals =	$999.39		$1,075.8662	$1,075.88	$1,075.90	$1,075.80