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	$145.54	3.799%	$151.0691	$151.07	$151.05	$151.10
Purchase #2	$105.76	6.534%	$112.6704	$112.67	$112.65	$112.70
Purchase #3	$97.51	11.699%	$108.9177	$108.92	$108.90	$108.90
Purchase #4	$222.74	5.456%	$234.8927	$234.89	$234.90	$234.90
Purchase #5	$220.47	4.849%	$231.1606	$231.16	$231.15	$231.20
Purchase #6	$119.27	7.164%	$127.8145	$127.81	$127.80	$127.80
Purchase #7	$110.71	7.203%	$118.6844	$118.68	$118.70	$118.70
7 purchase totals =	$1,022.00		$1,085.2094	$1,085.20	$1,085.15	$1,085.30