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	$127.68	11.431%	$142.2751	$142.28	$142.30	$142.30
Purchase #2	$98.43	11.554%	$109.8026	$109.80	$109.80	$109.80
Purchase #3	$72.91	9.766%	$80.0304	$80.03	$80.05	$80.00
Purchase #4	$208.34	4.845%	$218.4341	$218.43	$218.45	$218.40
Purchase #5	$116.28	11.403%	$129.5394	$129.54	$129.55	$129.50
Purchase #6	$100.33	11.198%	$111.565	$111.57	$111.55	$111.60
Purchase #7	$90.26	3.569%	$93.4814	$93.48	$93.50	$93.50
7 purchase totals =	$814.23		$885.1280	$885.13	$885.20	$885.10