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	$173.85	10.205%	$191.5914	$191.59	$191.60	$191.60
Purchase #2	$147.73	13.378%	$167.4933	$167.49	$167.50	$167.50
Purchase #3	$178.31	7.827%	$192.2663	$192.27	$192.25	$192.30
Purchase #4	$134.74	12.245%	$151.2389	$151.24	$151.25	$151.20
Purchase #5	$74.29	6.643%	$79.2251	$79.23	$79.25	$79.20
Purchase #6	$141.89	12.546%	$159.6915	$159.69	$159.70	$159.70
Purchase #7	$85.91	7.187%	$92.0844	$92.08	$92.10	$92.10
7 purchase totals =	$936.72		$1,033.5909	$1,033.59	$1,033.65	$1,033.60