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	$112.48	9.459%	$123.1195	$123.12	$123.10	$123.10
Purchase #2	$151.84	4.384%	$158.4967	$158.50	$158.50	$158.50
Purchase #3	$103.62	13.357%	$117.4605	$117.46	$117.45	$117.50
Purchase #4	$62.27	5.617%	$65.7677	$65.77	$65.75	$65.80
Purchase #5	$130.34	12.657%	$146.8371	$146.84	$146.85	$146.80
Purchase #6	$127.61	7.403%	$137.057	$137.06	$137.05	$137.10
Purchase #7	$234.83	12.601%	$264.4209	$264.42	$264.40	$264.40
7 purchase totals =	$922.99		$1,013.1594	$1,013.17	$1,013.10	$1,013.20