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	$191.40	12.133%	$214.6226	$214.62	$214.60	$214.60
Purchase #2	$140.72	11.302%	$156.6242	$156.62	$156.60	$156.60
Purchase #3	$105.84	4.255%	$110.3435	$110.34	$110.35	$110.30
Purchase #4	$204.58	12.507%	$230.1668	$230.17	$230.15	$230.20
Purchase #5	$100.42	9.233%	$109.6918	$109.69	$109.70	$109.70
Purchase #6	$211.25	11.644%	$235.848	$235.85	$235.85	$235.80
Purchase #7	$129.72	7.623%	$139.6086	$139.61	$139.60	$139.60
7 purchase totals =	$1,083.93		$1,196.9055	$1,196.90	$1,196.85	$1,196.80