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	$89.68	5.838%	$94.9155	$94.92	$94.90	$94.90
Purchase #2	$114.92	11.171%	$127.7577	$127.76	$127.75	$127.80
Purchase #3	$130.93	9.545%	$143.4273	$143.43	$143.45	$143.40
Purchase #4	$182.55	7.694%	$196.5954	$196.60	$196.60	$196.60
Purchase #5	$228.79	10.552%	$252.9319	$252.93	$252.95	$252.90
Purchase #6	$220.58	9.157%	$240.7785	$240.78	$240.80	$240.80
Purchase #7	$90.37	8.653%	$98.1897	$98.19	$98.20	$98.20
7 purchase totals =	$1,057.82		$1,154.5960	$1,154.61	$1,154.65	$1,154.60