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	$199.56	9.805%	$219.1269	$219.13	$219.15	$219.10
Purchase #2	$157.66	10.381%	$174.0267	$174.03	$174.05	$174.00
Purchase #3	$131.51	10.647%	$145.5119	$145.51	$145.50	$145.50
Purchase #4	$131.79	12.673%	$148.4917	$148.49	$148.50	$148.50
Purchase #5	$134.77	5.140%	$141.6972	$141.70	$141.70	$141.70
Purchase #6	$97.70	3.436%	$101.057	$101.06	$101.05	$101.10
Purchase #7	$115.85	13.519%	$131.5118	$131.51	$131.50	$131.50
7 purchase totals =	$968.84		$1,061.4232	$1,061.43	$1,061.45	$1,061.40