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	$131.83	10.680%	$145.9094	$145.91	$145.90	$145.90
Purchase #2	$159.33	4.859%	$167.0718	$167.07	$167.05	$167.10
Purchase #3	$63.37	9.463%	$69.3667	$69.37	$69.35	$69.40
Purchase #4	$163.42	13.771%	$185.9246	$185.92	$185.90	$185.90
Purchase #5	$21.83	3.577%	$22.6109	$22.61	$22.60	$22.60
Purchase #6	$228.28	3.441%	$236.1351	$236.14	$236.15	$236.10
Purchase #7	$244.52	4.564%	$255.6799	$255.68	$255.70	$255.70
7 purchase totals =	$1,012.58		$1,082.6984	$1,082.70	$1,082.65	$1,082.70