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	$54.34	9.601%	$59.5572	$59.56	$59.55	$59.60
Purchase #2	$61.51	6.486%	$65.4995	$65.50	$65.50	$65.50
Purchase #3	$28.57	4.304%	$29.7997	$29.80	$29.80	$29.80
Purchase #4	$155.41	3.764%	$161.2596	$161.26	$161.25	$161.30
Purchase #5	$235.92	3.702%	$244.6538	$244.65	$244.65	$244.70
Purchase #6	$99.60	5.538%	$105.1158	$105.12	$105.10	$105.10
Purchase #7	$160.38	7.155%	$171.8552	$171.86	$171.85	$171.90
7 purchase totals =	$795.73		$837.7408	$837.75	$837.70	$837.90