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	$186.89	7.293%	$200.5199	$200.52	$200.50	$200.50
Purchase #2	$104.67	13.341%	$118.634	$118.63	$118.65	$118.60
Purchase #3	$191.45	9.704%	$210.0283	$210.03	$210.05	$210.00
Purchase #4	$138.85	5.435%	$146.3965	$146.40	$146.40	$146.40
Purchase #5	$102.64	8.511%	$111.3757	$111.38	$111.40	$111.40
Purchase #6	$209.70	3.844%	$217.7609	$217.76	$217.75	$217.80
Purchase #7	$136.60	7.291%	$146.5595	$146.56	$146.55	$146.60
7 purchase totals =	$1,070.80		$1,151.2748	$1,151.28	$1,151.30	$1,151.30