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	$187.92	12.757%	$211.893	$211.89	$211.90	$211.90
Purchase #2	$35.52	5.470%	$37.4629	$37.46	$37.45	$37.50
Purchase #3	$11.93	11.192%	$13.2652	$13.27	$13.25	$13.30
Purchase #4	$87.50	3.140%	$90.2475	$90.25	$90.25	$90.20
Purchase #5	$144.64	10.639%	$160.0282	$160.03	$160.05	$160.00
Purchase #6	$204.28	5.397%	$215.305	$215.31	$215.30	$215.30
Purchase #7	$188.87	12.345%	$212.186	$212.19	$212.20	$212.20
7 purchase totals =	$860.66		$940.3878	$940.40	$940.40	$940.40