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	$97.89	13.556%	$111.16	$111.16	$111.15	$111.20
Purchase #2	$48.44	13.248%	$54.8573	$54.86	$54.85	$54.90
Purchase #3	$74.96	5.863%	$79.3549	$79.35	$79.35	$79.40
Purchase #4	$86.58	6.485%	$92.1947	$92.19	$92.20	$92.20
Purchase #5	$60.33	9.256%	$65.9141	$65.91	$65.90	$65.90
Purchase #6	$134.76	8.115%	$145.6958	$145.70	$145.70	$145.70
Purchase #7	$33.75	13.847%	$38.4234	$38.42	$38.40	$38.40
7 purchase totals =	$536.71		$587.6002	$587.59	$587.55	$587.70