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	$92.52	7.730%	$99.6718	$99.67	$99.65	$99.70
Purchase #2	$62.70	13.384%	$71.0918	$71.09	$71.10	$71.10
Purchase #3	$11.94	12.234%	$13.4007	$13.40	$13.40	$13.40
Purchase #4	$94.71	9.195%	$103.4186	$103.42	$103.40	$103.40
Purchase #5	$222.70	3.123%	$229.6549	$229.65	$229.65	$229.70
Purchase #6	$34.27	11.153%	$38.0921	$38.09	$38.10	$38.10
Purchase #7	$19.45	6.678%	$20.7489	$20.75	$20.75	$20.70
7 purchase totals =	$538.29		$576.0788	$576.07	$576.05	$576.10