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	$12.90	12.296%	$14.4862	$14.49	$14.50	$14.50
Purchase #2	$67.32	6.477%	$71.6803	$71.68	$71.70	$71.70
Purchase #3	$5.79	10.123%	$6.3761	$6.38	$6.40	$6.40
Purchase #4	$45.86	13.699%	$52.1424	$52.14	$52.15	$52.10
Purchase #5	$95.53	5.297%	$100.5902	$100.59	$100.60	$100.60
Purchase #6	$163.77	10.336%	$180.6973	$180.70	$180.70	$180.70
Purchase #7	$135.90	4.175%	$141.5738	$141.57	$141.55	$141.60
7 purchase totals =	$527.07		$567.5463	$567.55	$567.60	$567.60