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	$183.46	9.391%	$200.6887	$200.69	$200.70	$200.70
Purchase #2	$111.37	12.145%	$124.8959	$124.90	$124.90	$124.90
Purchase #3	$184.72	4.285%	$192.6353	$192.64	$192.65	$192.60
Purchase #4	$146.32	3.215%	$151.0242	$151.02	$151.00	$151.00
Purchase #5	$222.89	6.456%	$237.2798	$237.28	$237.30	$237.30
Purchase #6	$82.46	8.725%	$89.6546	$89.65	$89.65	$89.70
Purchase #7	$43.82	3.802%	$45.486	$45.49	$45.50	$45.50
7 purchase totals =	$975.04		$1,041.6645	$1,041.67	$1,041.70	$1,041.70