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	$157.40	5.212%	$165.6037	$165.60	$165.60	$165.60
Purchase #2	$112.46	4.337%	$117.3374	$117.34	$117.35	$117.30
Purchase #3	$122.30	8.481%	$132.6723	$132.67	$132.65	$132.70
Purchase #4	$66.62	12.830%	$75.1673	$75.17	$75.15	$75.20
Purchase #5	$194.72	13.633%	$221.2662	$221.27	$221.25	$221.30
Purchase #6	$51.51	6.404%	$54.8087	$54.81	$54.80	$54.80
Purchase #7	$219.60	13.807%	$249.9202	$249.92	$249.90	$249.90
7 purchase totals =	$924.61		$1,016.7758	$1,016.78	$1,016.70	$1,016.80