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	$215.41	9.625%	$236.1432	$236.14	$236.15	$236.10
Purchase #2	$152.83	3.508%	$158.1913	$158.19	$158.20	$158.20
Purchase #3	$82.78	9.569%	$90.7012	$90.70	$90.70	$90.70
Purchase #4	$57.25	7.194%	$61.3686	$61.37	$61.35	$61.40
Purchase #5	$122.53	4.242%	$127.7277	$127.73	$127.75	$127.70
Purchase #6	$145.53	11.849%	$162.7738	$162.77	$162.75	$162.80
Purchase #7	$249.78	5.310%	$263.0433	$263.04	$263.05	$263.00
7 purchase totals =	$1,026.11		$1,099.9491	$1,099.94	$1,099.95	$1,099.90