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	$47.25	6.195%	$50.1771	$50.18	$50.20	$50.20
Purchase #2	$9.46	11.792%	$10.5755	$10.58	$10.60	$10.60
Purchase #3	$170.77	10.588%	$188.8511	$188.85	$188.85	$188.90
Purchase #4	$64.90	11.426%	$72.3155	$72.32	$72.30	$72.30
Purchase #5	$81.81	4.666%	$85.6273	$85.63	$85.65	$85.60
Purchase #6	$111.77	3.815%	$116.034	$116.03	$116.05	$116.00
Purchase #7	$100.51	6.539%	$107.0823	$107.08	$107.10	$107.10
7 purchase totals =	$586.47		$630.6628	$630.67	$630.75	$630.70