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	$158.96	13.527%	$180.4625	$180.46	$180.45	$180.50
Purchase #2	$96.48	12.352%	$108.3972	$108.40	$108.40	$108.40
Purchase #3	$83.90	7.492%	$90.1858	$90.19	$90.20	$90.20
Purchase #4	$88.68	13.106%	$100.3024	$100.30	$100.30	$100.30
Purchase #5	$11.75	11.692%	$13.1238	$13.12	$13.10	$13.10
Purchase #6	$40.64	5.285%	$42.7878	$42.79	$42.80	$42.80
Purchase #7	$177.46	4.631%	$185.6782	$185.68	$185.70	$185.70
7 purchase totals =	$657.87		$720.9377	$720.94	$720.95	$721.00