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	$191.52	12.597%	$215.6458	$215.65	$215.65	$215.60
Purchase #2	$80.43	7.429%	$86.4051	$86.41	$86.40	$86.40
Purchase #3	$8.94	13.319%	$10.1307	$10.13	$10.15	$10.10
Purchase #4	$131.94	11.521%	$147.1408	$147.14	$147.15	$147.10
Purchase #5	$50.44	12.193%	$56.5901	$56.59	$56.60	$56.60
Purchase #6	$115.91	9.860%	$127.3387	$127.34	$127.35	$127.30
Purchase #7	$47.43	13.169%	$53.6761	$53.68	$53.70	$53.70
7 purchase totals =	$626.61		$696.9273	$696.94	$697.00	$696.80