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	$215.87	13.323%	$244.6304	$244.63	$244.65	$244.60
Purchase #2	$241.80	10.254%	$266.5942	$266.59	$266.60	$266.60
Purchase #3	$147.54	4.848%	$154.6927	$154.69	$154.70	$154.70
Purchase #4	$91.81	12.325%	$103.1256	$103.13	$103.15	$103.10
Purchase #5	$119.83	6.614%	$127.7556	$127.76	$127.75	$127.80
Purchase #6	$109.72	12.464%	$123.3955	$123.40	$123.40	$123.40
Purchase #7	$83.67	6.635%	$89.2215	$89.22	$89.20	$89.20
7 purchase totals =	$1,010.24		$1,109.4155	$1,109.42	$1,109.45	$1,109.40