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	$162.39	8.391%	$176.0161	$176.02	$176.00	$176.00
Purchase #2	$112.43	13.556%	$127.671	$127.67	$127.65	$127.70
Purchase #3	$16.60	13.706%	$18.8752	$18.88	$18.90	$18.90
Purchase #4	$188.89	13.784%	$214.9266	$214.93	$214.95	$214.90
Purchase #5	$142.79	5.760%	$151.0147	$151.01	$151.00	$151.00
Purchase #6	$158.29	10.741%	$175.2919	$175.29	$175.30	$175.30
Purchase #7	$67.68	6.374%	$71.9939	$71.99	$72.00	$72.00
7 purchase totals =	$849.07		$935.7894	$935.79	$935.80	$935.80