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	$143.54	4.671%	$150.2448	$150.24	$150.25	$150.20
Purchase #2	$165.59	8.555%	$179.7562	$179.76	$179.75	$179.80
Purchase #3	$62.90	11.675%	$70.2436	$70.24	$70.25	$70.20
Purchase #4	$41.27	10.501%	$45.6038	$45.60	$45.60	$45.60
Purchase #5	$47.77	12.519%	$53.7503	$53.75	$53.75	$53.80
Purchase #6	$95.82	3.271%	$98.9543	$98.95	$98.95	$99.00
Purchase #7	$115.50	6.448%	$122.9474	$122.95	$122.95	$122.90
7 purchase totals =	$672.39		$721.5004	$721.49	$721.50	$721.50