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	$150.69	4.461%	$157.4123	$157.41	$157.40	$157.40
Purchase #2	$146.88	10.565%	$162.3979	$162.40	$162.40	$162.40
Purchase #3	$175.47	8.748%	$190.8201	$190.82	$190.80	$190.80
Purchase #4	$95.34	13.767%	$108.4655	$108.47	$108.45	$108.50
Purchase #5	$46.96	8.472%	$50.9385	$50.94	$50.95	$50.90
Purchase #6	$243.60	4.372%	$254.2502	$254.25	$254.25	$254.30
Purchase #7	$52.96	12.844%	$59.7622	$59.76	$59.75	$59.80
7 purchase totals =	$911.90		$984.0467	$984.05	$984.00	$984.10