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	$60.64	7.634%	$65.2693	$65.27	$65.25	$65.30
Purchase #2	$91.84	5.447%	$96.8425	$96.84	$96.85	$96.80
Purchase #3	$36.42	8.177%	$39.3981	$39.40	$39.40	$39.40
Purchase #4	$215.39	6.363%	$229.0953	$229.10	$229.10	$229.10
Purchase #5	$132.87	13.837%	$151.2552	$151.26	$151.25	$151.30
Purchase #6	$151.81	13.362%	$172.0949	$172.09	$172.10	$172.10
Purchase #7	$100.66	6.815%	$107.52	$107.52	$107.50	$107.50
7 purchase totals =	$789.63		$861.4753	$861.48	$861.45	$861.50