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	$103.74	7.162%	$111.1699	$111.17	$111.15	$111.20
Purchase #2	$51.74	4.328%	$53.9793	$53.98	$54.00	$54.00
Purchase #3	$76.27	9.728%	$83.6895	$83.69	$83.70	$83.70
Purchase #4	$56.78	4.409%	$59.2834	$59.28	$59.30	$59.30
Purchase #5	$63.50	7.688%	$68.3819	$68.38	$68.40	$68.40
Purchase #6	$142.89	12.504%	$160.757	$160.76	$160.75	$160.80
Purchase #7	$169.84	3.706%	$176.1343	$176.13	$176.15	$176.10
7 purchase totals =	$664.76		$713.3953	$713.39	$713.45	$713.50