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	$40.74	11.368%	$45.3713	$45.37	$45.35	$45.40
Purchase #2	$152.58	12.103%	$171.0468	$171.05	$171.05	$171.00
Purchase #3	$89.32	9.697%	$97.9814	$97.98	$98.00	$98.00
Purchase #4	$127.80	13.321%	$144.8242	$144.82	$144.80	$144.80
Purchase #5	$178.33	7.857%	$192.3414	$192.34	$192.35	$192.30
Purchase #6	$47.78	13.857%	$54.4009	$54.40	$54.40	$54.40
Purchase #7	$194.52	8.288%	$210.6418	$210.64	$210.65	$210.60
7 purchase totals =	$831.07		$916.6078	$916.60	$916.60	$916.50