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	$149.66	4.528%	$156.4366	$156.44	$156.45	$156.40
Purchase #2	$221.76	9.703%	$243.2774	$243.28	$243.30	$243.30
Purchase #3	$176.89	12.774%	$199.4859	$199.49	$199.50	$199.50
Purchase #4	$60.32	6.719%	$64.3729	$64.37	$64.35	$64.40
Purchase #5	$155.73	11.188%	$173.1531	$173.15	$173.15	$173.20
Purchase #6	$80.41	6.733%	$85.824	$85.82	$85.80	$85.80
Purchase #7	$86.99	10.247%	$95.9039	$95.90	$95.90	$95.90
7 purchase totals =	$931.76		$1,018.4538	$1,018.45	$1,018.45	$1,018.50