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	$196.28	4.373%	$204.8633	$204.86	$204.85	$204.90
Purchase #2	$127.36	5.774%	$134.7138	$134.71	$134.70	$134.70
Purchase #3	$170.78	8.477%	$185.257	$185.26	$185.25	$185.30
Purchase #4	$177.60	10.725%	$196.6476	$196.65	$196.65	$196.60
Purchase #5	$249.35	10.384%	$275.2425	$275.24	$275.25	$275.20
Purchase #6	$165.31	9.170%	$180.4689	$180.47	$180.45	$180.50
Purchase #7	$49.65	6.684%	$52.9686	$52.97	$52.95	$53.00
7 purchase totals =	$1,136.33		$1,230.1617	$1,230.16	$1,230.10	$1,230.20