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	$229.42	4.776%	$240.3771	$240.38	$240.40	$240.40
Purchase #2	$161.27	6.253%	$171.3542	$171.35	$171.35	$171.40
Purchase #3	$166.90	3.613%	$172.9301	$172.93	$172.95	$172.90
Purchase #4	$164.66	10.802%	$182.4466	$182.45	$182.45	$182.40
Purchase #5	$18.31	13.233%	$20.733	$20.73	$20.75	$20.70
Purchase #6	$222.50	9.835%	$244.3829	$244.38	$244.40	$244.40
Purchase #7	$203.35	13.413%	$230.6253	$230.63	$230.65	$230.60
7 purchase totals =	$1,166.41		$1,262.8492	$1,262.85	$1,262.95	$1,262.80