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	$205.46	11.520%	$229.129	$229.13	$229.15	$229.10
Purchase #2	$195.50	4.754%	$204.7941	$204.79	$204.80	$204.80
Purchase #3	$52.90	6.288%	$56.2264	$56.23	$56.25	$56.20
Purchase #4	$68.94	8.550%	$74.8344	$74.83	$74.85	$74.80
Purchase #5	$142.38	6.370%	$151.4496	$151.45	$151.45	$151.40
Purchase #6	$91.45	10.167%	$100.7477	$100.75	$100.75	$100.70
Purchase #7	$105.97	5.219%	$111.5006	$111.50	$111.50	$111.50
7 purchase totals =	$862.60		$928.6818	$928.68	$928.75	$928.50