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	$236.29	11.233%	$262.8325	$262.83	$262.85	$262.80
Purchase #2	$41.69	12.178%	$46.767	$46.77	$46.75	$46.80
Purchase #3	$223.71	13.622%	$254.1838	$254.18	$254.20	$254.20
Purchase #4	$249.95	5.439%	$263.5448	$263.54	$263.55	$263.50
Purchase #5	$38.87	4.683%	$40.6903	$40.69	$40.70	$40.70
Purchase #6	$89.54	10.625%	$99.0536	$99.05	$99.05	$99.10
Purchase #7	$46.29	4.523%	$48.3837	$48.38	$48.40	$48.40
7 purchase totals =	$926.34		$1,015.4557	$1,015.44	$1,015.50	$1,015.50