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	$130.50	10.587%	$144.316	$144.32	$144.30	$144.30
Purchase #2	$155.59	13.290%	$176.2679	$176.27	$176.25	$176.30
Purchase #3	$202.25	5.341%	$213.0522	$213.05	$213.05	$213.10
Purchase #4	$134.52	12.334%	$151.1117	$151.11	$151.10	$151.10
Purchase #5	$102.55	13.246%	$116.1338	$116.13	$116.15	$116.10
Purchase #6	$99.44	11.606%	$110.981	$110.98	$111.00	$111.00
Purchase #7	$60.68	9.594%	$66.5016	$66.50	$66.50	$66.50
7 purchase totals =	$885.53		$978.3642	$978.36	$978.35	$978.40