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	$36.71	4.274%	$38.279	$38.28	$38.30	$38.30
Purchase #2	$19.81	13.393%	$22.4632	$22.46	$22.45	$22.50
Purchase #3	$250.82	3.603%	$259.857	$259.86	$259.85	$259.90
Purchase #4	$212.64	11.558%	$237.2169	$237.22	$237.20	$237.20
Purchase #5	$49.26	8.136%	$53.2678	$53.27	$53.25	$53.30
Purchase #6	$40.58	6.311%	$43.141	$43.14	$43.15	$43.10
Purchase #7	$111.69	13.613%	$126.8944	$126.89	$126.90	$126.90
7 purchase totals =	$721.51		$781.1193	$781.12	$781.10	$781.20