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	$55.98	9.340%	$61.2085	$61.21	$61.20	$61.20
Purchase #2	$163.70	12.784%	$184.6274	$184.63	$184.65	$184.60
Purchase #3	$105.29	5.549%	$111.1325	$111.13	$111.15	$111.10
Purchase #4	$204.76	3.210%	$211.3328	$211.33	$211.35	$211.30
Purchase #5	$112.68	10.825%	$124.8776	$124.88	$124.90	$124.90
Purchase #6	$50.93	10.447%	$56.2507	$56.25	$56.25	$56.30
Purchase #7	$111.27	6.558%	$118.5671	$118.57	$118.55	$118.60
7 purchase totals =	$804.61		$867.9966	$868.00	$868.05	$868.00