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	$92.42	9.684%	$101.37	$101.37	$101.35	$101.40
Purchase #2	$127.49	7.490%	$137.039	$137.04	$137.05	$137.00
Purchase #3	$221.97	5.205%	$233.5235	$233.52	$233.50	$233.50
Purchase #4	$49.46	6.180%	$52.5166	$52.52	$52.50	$52.50
Purchase #5	$105.58	5.674%	$111.5706	$111.57	$111.55	$111.60
Purchase #6	$14.42	4.368%	$15.0499	$15.05	$15.05	$15.00
Purchase #7	$156.41	10.589%	$172.9723	$172.97	$172.95	$173.00
7 purchase totals =	$767.75		$824.0419	$824.04	$823.95	$824.00