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	$133.47	8.127%	$144.3171	$144.32	$144.30	$144.30
Purchase #2	$215.82	4.162%	$224.8024	$224.80	$224.80	$224.80
Purchase #3	$71.65	8.165%	$77.5002	$77.50	$77.50	$77.50
Purchase #4	$116.68	10.319%	$128.7202	$128.72	$128.70	$128.70
Purchase #5	$214.42	8.695%	$233.0638	$233.06	$233.05	$233.10
Purchase #6	$155.69	11.396%	$173.4324	$173.43	$173.45	$173.40
Purchase #7	$111.76	6.240%	$118.7338	$118.73	$118.75	$118.70
7 purchase totals =	$1,019.49		$1,100.5699	$1,100.56	$1,100.55	$1,100.50