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	$149.88	5.640%	$158.3332	$158.33	$158.35	$158.30
Purchase #2	$180.92	7.567%	$194.6102	$194.61	$194.60	$194.60
Purchase #3	$167.61	8.494%	$181.8468	$181.85	$181.85	$181.80
Purchase #4	$209.54	9.752%	$229.9743	$229.97	$229.95	$230.00
Purchase #5	$45.28	6.648%	$48.2902	$48.29	$48.30	$48.30
Purchase #6	$57.53	3.367%	$59.467	$59.47	$59.45	$59.50
Purchase #7	$99.39	13.868%	$113.1734	$113.17	$113.15	$113.20
7 purchase totals =	$910.15		$985.6951	$985.69	$985.65	$985.70