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	$166.70	3.631%	$172.7529	$172.75	$172.75	$172.80
Purchase #2	$246.42	4.493%	$257.4917	$257.49	$257.50	$257.50
Purchase #3	$35.68	7.807%	$38.4655	$38.47	$38.45	$38.50
Purchase #4	$181.44	10.316%	$200.1574	$200.16	$200.15	$200.20
Purchase #5	$70.50	11.393%	$78.5321	$78.53	$78.55	$78.50
Purchase #6	$244.71	4.506%	$255.7366	$255.74	$255.75	$255.70
Purchase #7	$101.92	4.269%	$106.271	$106.27	$106.25	$106.30
7 purchase totals =	$1,047.37		$1,109.4072	$1,109.41	$1,109.40	$1,109.50