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	$24.51	3.860%	$25.4561	$25.46	$25.45	$25.50
Purchase #2	$107.82	10.303%	$118.9287	$118.93	$118.95	$118.90
Purchase #3	$217.55	12.341%	$244.3978	$244.40	$244.40	$244.40
Purchase #4	$172.93	9.765%	$189.8166	$189.82	$189.80	$189.80
Purchase #5	$190.61	11.447%	$212.4291	$212.43	$212.45	$212.40
Purchase #6	$212.69	10.261%	$234.5141	$234.51	$234.50	$234.50
Purchase #7	$118.49	5.137%	$124.5768	$124.58	$124.60	$124.60
7 purchase totals =	$1,044.60		$1,150.1192	$1,150.13	$1,150.15	$1,150.10