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	$148.29	5.307%	$156.1598	$156.16	$156.15	$156.20
Purchase #2	$217.59	3.194%	$224.5398	$224.54	$224.55	$224.50
Purchase #3	$192.43	6.754%	$205.4267	$205.43	$205.45	$205.40
Purchase #4	$50.46	8.800%	$54.9005	$54.90	$54.90	$54.90
Purchase #5	$189.60	3.771%	$196.7498	$196.75	$196.75	$196.70
Purchase #6	$108.26	4.616%	$113.2573	$113.26	$113.25	$113.30
Purchase #7	$178.91	3.532%	$185.2291	$185.23	$185.25	$185.20
7 purchase totals =	$1,085.54		$1,136.2630	$1,136.27	$1,136.30	$1,136.20