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	$184.78	11.412%	$205.8671	$205.87	$205.85	$205.90
Purchase #2	$75.47	12.865%	$85.1792	$85.18	$85.20	$85.20
Purchase #3	$250.99	12.662%	$282.7704	$282.77	$282.75	$282.80
Purchase #4	$146.27	12.639%	$164.7571	$164.76	$164.75	$164.80
Purchase #5	$114.31	11.343%	$127.2762	$127.28	$127.30	$127.30
Purchase #6	$70.60	11.641%	$78.8185	$78.82	$78.80	$78.80
Purchase #7	$29.55	3.204%	$30.4968	$30.50	$30.50	$30.50
7 purchase totals =	$871.97		$975.1653	$975.18	$975.15	$975.30