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	$110.47	5.141%	$116.1493	$116.15	$116.15	$116.10
Purchase #2	$37.26	8.759%	$40.5236	$40.52	$40.50	$40.50
Purchase #3	$228.79	7.479%	$245.9012	$245.90	$245.90	$245.90
Purchase #4	$122.42	6.456%	$130.3234	$130.32	$130.30	$130.30
Purchase #5	$116.44	13.792%	$132.4994	$132.50	$132.50	$132.50
Purchase #6	$81.39	7.595%	$87.5716	$87.57	$87.55	$87.60
Purchase #7	$110.62	11.572%	$123.4209	$123.42	$123.40	$123.40
7 purchase totals =	$807.39		$876.3894	$876.38	$876.30	$876.30