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	$159.28	8.502%	$172.822	$172.82	$172.80	$172.80
Purchase #2	$165.72	7.798%	$178.6428	$178.64	$178.65	$178.60
Purchase #3	$191.56	4.788%	$200.7319	$200.73	$200.75	$200.70
Purchase #4	$140.76	10.549%	$155.6088	$155.61	$155.60	$155.60
Purchase #5	$163.40	13.368%	$185.2433	$185.24	$185.25	$185.20
Purchase #6	$177.92	12.588%	$200.3166	$200.32	$200.30	$200.30
Purchase #7	$213.34	11.112%	$237.0463	$237.05	$237.05	$237.00
7 purchase totals =	$1,211.98		$1,330.4117	$1,330.41	$1,330.40	$1,330.20