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	$244.94	11.502%	$273.113	$273.11	$273.10	$273.10
Purchase #2	$29.38	9.259%	$32.1003	$32.10	$32.10	$32.10
Purchase #3	$159.36	4.268%	$166.1615	$166.16	$166.15	$166.20
Purchase #4	$156.34	5.722%	$165.2858	$165.29	$165.30	$165.30
Purchase #5	$173.34	10.693%	$191.8752	$191.88	$191.90	$191.90
Purchase #6	$66.56	9.429%	$72.8359	$72.84	$72.85	$72.80
Purchase #7	$138.60	4.589%	$144.9604	$144.96	$144.95	$145.00
7 purchase totals =	$968.52		$1,046.3321	$1,046.34	$1,046.35	$1,046.40