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	$134.70	8.175%	$145.7117	$145.71	$145.70	$145.70
Purchase #2	$34.75	7.783%	$37.4546	$37.45	$37.45	$37.50
Purchase #3	$129.87	10.159%	$143.0635	$143.06	$143.05	$143.10
Purchase #4	$79.45	3.382%	$82.137	$82.14	$82.15	$82.10
Purchase #5	$140.51	9.160%	$153.3807	$153.38	$153.40	$153.40
Purchase #6	$18.68	8.656%	$20.2969	$20.30	$20.30	$20.30
Purchase #7	$28.80	8.253%	$31.1769	$31.18	$31.20	$31.20
7 purchase totals =	$566.76		$613.2213	$613.22	$613.25	$613.30