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	$241.39	9.137%	$263.4458	$263.45	$263.45	$263.40
Purchase #2	$220.54	13.651%	$250.6459	$250.65	$250.65	$250.60
Purchase #3	$40.80	13.758%	$46.4133	$46.41	$46.40	$46.40
Purchase #4	$172.25	12.366%	$193.5504	$193.55	$193.55	$193.60
Purchase #5	$39.84	7.381%	$42.7806	$42.78	$42.80	$42.80
Purchase #6	$49.59	13.806%	$56.4364	$56.44	$56.45	$56.40
Purchase #7	$229.69	7.466%	$246.8387	$246.84	$246.85	$246.80
7 purchase totals =	$994.10		$1,100.1111	$1,100.12	$1,100.15	$1,100.00