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	$214.68	3.253%	$221.6635	$221.66	$221.65	$221.70
Purchase #2	$6.25	13.152%	$7.072	$7.07	$7.05	$7.10
Purchase #3	$199.81	5.117%	$210.0343	$210.03	$210.05	$210.00
Purchase #4	$104.75	6.703%	$111.7714	$111.77	$111.75	$111.80
Purchase #5	$91.81	13.193%	$103.9225	$103.92	$103.90	$103.90
Purchase #6	$138.29	5.543%	$145.9554	$145.96	$145.95	$146.00
Purchase #7	$60.30	11.842%	$67.4407	$67.44	$67.45	$67.40
7 purchase totals =	$815.89		$867.8598	$867.85	$867.80	$867.90