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	$132.41	6.818%	$141.4377	$141.44	$141.45	$141.40
Purchase #2	$177.69	4.196%	$185.1459	$185.15	$185.15	$185.10
Purchase #3	$150.94	7.184%	$161.7835	$161.78	$161.80	$161.80
Purchase #4	$79.41	10.326%	$87.6099	$87.61	$87.60	$87.60
Purchase #5	$194.59	11.671%	$217.3006	$217.30	$217.30	$217.30
Purchase #6	$100.39	3.113%	$103.5151	$103.52	$103.50	$103.50
Purchase #7	$204.80	8.446%	$222.0974	$222.10	$222.10	$222.10
7 purchase totals =	$1,040.23		$1,118.8901	$1,118.90	$1,118.90	$1,118.80