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	$160.93	5.318%	$169.4883	$169.49	$169.50	$169.50
Purchase #2	$70.52	8.610%	$76.5918	$76.59	$76.60	$76.60
Purchase #3	$136.31	9.411%	$149.1381	$149.14	$149.15	$149.10
Purchase #4	$63.99	11.487%	$71.3405	$71.34	$71.35	$71.30
Purchase #5	$53.95	4.314%	$56.2774	$56.28	$56.30	$56.30
Purchase #6	$11.73	4.405%	$12.2467	$12.25	$12.25	$12.20
Purchase #7	$79.70	12.764%	$89.8729	$89.87	$89.85	$89.90
7 purchase totals =	$577.13		$624.9557	$624.96	$625.00	$624.90