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	$37.69	7.312%	$40.4459	$40.45	$40.45	$40.40
Purchase #2	$50.66	4.388%	$52.883	$52.88	$52.90	$52.90
Purchase #3	$96.88	11.548%	$108.0677	$108.07	$108.05	$108.10
Purchase #4	$109.62	4.134%	$114.1517	$114.15	$114.15	$114.20
Purchase #5	$211.64	7.836%	$228.2241	$228.22	$228.20	$228.20
Purchase #6	$177.51	10.806%	$196.6917	$196.69	$196.70	$196.70
Purchase #7	$138.65	4.369%	$144.7076	$144.71	$144.70	$144.70
7 purchase totals =	$822.65		$885.1717	$885.17	$885.15	$885.20