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	$102.86	8.831%	$111.9436	$111.94	$111.95	$111.90
Purchase #2	$110.46	5.461%	$116.4922	$116.49	$116.50	$116.50
Purchase #3	$72.91	13.585%	$82.8148	$82.81	$82.80	$82.80
Purchase #4	$136.33	11.272%	$151.6971	$151.70	$151.70	$151.70
Purchase #5	$243.47	4.721%	$254.9642	$254.96	$254.95	$255.00
Purchase #6	$14.32	3.192%	$14.7771	$14.78	$14.80	$14.80
Purchase #7	$69.81	4.195%	$72.7385	$72.74	$72.75	$72.70
7 purchase totals =	$750.16		$805.4275	$805.42	$805.45	$805.40