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	$60.59	3.301%	$62.5901	$62.59	$62.60	$62.60
Purchase #2	$100.90	8.111%	$109.084	$109.08	$109.10	$109.10
Purchase #3	$100.60	11.625%	$112.2948	$112.29	$112.30	$112.30
Purchase #4	$219.28	7.613%	$235.9738	$235.97	$235.95	$236.00
Purchase #5	$80.35	13.240%	$90.9883	$90.99	$91.00	$91.00
Purchase #6	$22.97	11.625%	$25.6403	$25.64	$25.65	$25.60
Purchase #7	$156.40	6.350%	$166.3314	$166.33	$166.35	$166.30
7 purchase totals =	$741.09		$802.9027	$802.89	$802.95	$802.90