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	$224.77	8.298%	$243.4214	$243.42	$243.40	$243.40
Purchase #2	$83.53	8.472%	$90.6067	$90.61	$90.60	$90.60
Purchase #3	$165.87	11.553%	$185.033	$185.03	$185.05	$185.00
Purchase #4	$163.27	8.104%	$176.5014	$176.50	$176.50	$176.50
Purchase #5	$148.58	11.640%	$165.8747	$165.87	$165.85	$165.90
Purchase #6	$130.67	12.160%	$146.5595	$146.56	$146.55	$146.60
Purchase #7	$60.95	5.279%	$64.1676	$64.17	$64.15	$64.20
7 purchase totals =	$977.64		$1,072.1643	$1,072.16	$1,072.10	$1,072.20