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	$46.54	3.526%	$48.181	$48.18	$48.20	$48.20
Purchase #2	$30.83	9.808%	$33.8538	$33.85	$33.85	$33.90
Purchase #3	$146.38	6.551%	$155.9694	$155.97	$155.95	$156.00
Purchase #4	$219.92	12.843%	$248.1643	$248.16	$248.15	$248.20
Purchase #5	$100.87	12.671%	$113.6512	$113.65	$113.65	$113.70
Purchase #6	$122.26	4.607%	$127.8925	$127.89	$127.90	$127.90
Purchase #7	$91.34	3.712%	$94.7305	$94.73	$94.75	$94.70
7 purchase totals =	$758.14		$822.4427	$822.43	$822.45	$822.60