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	$229.45	11.611%	$256.0914	$256.09	$256.10	$256.10
Purchase #2	$117.50	12.790%	$132.5283	$132.53	$132.55	$132.50
Purchase #3	$54.49	8.428%	$59.0824	$59.08	$59.10	$59.10
Purchase #4	$242.79	3.688%	$251.7441	$251.74	$251.75	$251.70
Purchase #5	$99.92	11.284%	$111.195	$111.20	$111.20	$111.20
Purchase #6	$143.98	4.446%	$150.3814	$150.38	$150.40	$150.40
Purchase #7	$222.94	10.471%	$246.284	$246.28	$246.30	$246.30
7 purchase totals =	$1,111.07		$1,207.3066	$1,207.30	$1,207.40	$1,207.30