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	$175.78	8.729%	$191.1238	$191.12	$191.10	$191.10
Purchase #2	$145.85	4.395%	$152.2601	$152.26	$152.25	$152.30
Purchase #3	$112.99	11.385%	$125.8539	$125.85	$125.85	$125.90
Purchase #4	$185.52	5.719%	$196.1299	$196.13	$196.15	$196.10
Purchase #5	$112.34	8.848%	$122.2798	$122.28	$122.30	$122.30
Purchase #6	$107.73	3.537%	$111.5404	$111.54	$111.55	$111.50
Purchase #7	$167.29	12.748%	$188.6161	$188.62	$188.60	$188.60
7 purchase totals =	$1,007.50		$1,087.8040	$1,087.80	$1,087.80	$1,087.80