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	$80.79	7.420%	$86.7846	$86.78	$86.80	$86.80
Purchase #2	$100.64	10.603%	$111.3109	$111.31	$111.30	$111.30
Purchase #3	$32.41	11.766%	$36.2234	$36.22	$36.20	$36.20
Purchase #4	$211.75	6.171%	$224.8171	$224.82	$224.80	$224.80
Purchase #5	$202.55	13.650%	$230.1981	$230.20	$230.20	$230.20
Purchase #6	$45.76	10.531%	$50.579	$50.58	$50.60	$50.60
Purchase #7	$55.38	11.839%	$61.9364	$61.94	$61.95	$61.90
7 purchase totals =	$729.28		$801.8495	$801.85	$801.85	$801.80