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	$226.37	13.552%	$257.0477	$257.05	$257.05	$257.00
Purchase #2	$162.51	6.173%	$172.5417	$172.54	$172.55	$172.50
Purchase #3	$40.78	12.181%	$45.7474	$45.75	$45.75	$45.70
Purchase #4	$171.82	10.658%	$190.1326	$190.13	$190.15	$190.10
Purchase #5	$127.32	10.212%	$140.3219	$140.32	$140.30	$140.30
Purchase #6	$117.39	9.707%	$128.785	$128.79	$128.80	$128.80
Purchase #7	$96.45	8.228%	$104.3859	$104.39	$104.40	$104.40
7 purchase totals =	$942.64		$1,038.9622	$1,038.97	$1,039.00	$1,038.80