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	$88.31	10.372%	$97.4695	$97.47	$97.45	$97.50
Purchase #2	$91.86	8.657%	$99.8123	$99.81	$99.80	$99.80
Purchase #3	$51.49	4.291%	$53.6994	$53.70	$53.70	$53.70
Purchase #4	$30.27	3.470%	$31.3204	$31.32	$31.30	$31.30
Purchase #5	$128.74	10.730%	$142.5538	$142.55	$142.55	$142.60
Purchase #6	$127.82	13.210%	$144.705	$144.71	$144.70	$144.70
Purchase #7	$63.58	3.198%	$65.6133	$65.61	$65.60	$65.60
7 purchase totals =	$582.07		$635.1737	$635.17	$635.10	$635.20