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	$136.57	11.102%	$151.732	$151.73	$151.75	$151.70
Purchase #2	$202.35	9.615%	$221.806	$221.81	$221.80	$221.80
Purchase #3	$187.57	4.638%	$196.2695	$196.27	$196.25	$196.30
Purchase #4	$133.36	8.193%	$144.2862	$144.29	$144.30	$144.30
Purchase #5	$143.87	13.858%	$163.8075	$163.81	$163.80	$163.80
Purchase #6	$49.81	7.739%	$53.6648	$53.66	$53.65	$53.70
Purchase #7	$64.42	11.776%	$72.0061	$72.01	$72.00	$72.00
7 purchase totals =	$917.95		$1,003.5721	$1,003.58	$1,003.55	$1,003.60