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	$164.79	4.634%	$172.4264	$172.43	$172.45	$172.40
Purchase #2	$147.29	12.181%	$165.2314	$165.23	$165.25	$165.20
Purchase #3	$250.58	13.769%	$285.0824	$285.08	$285.10	$285.10
Purchase #4	$244.93	5.379%	$258.1048	$258.10	$258.10	$258.10
Purchase #5	$134.70	11.743%	$150.5178	$150.52	$150.50	$150.50
Purchase #6	$46.72	12.238%	$52.4376	$52.44	$52.45	$52.40
Purchase #7	$167.36	9.198%	$182.7538	$182.75	$182.75	$182.80
7 purchase totals =	$1,156.37		$1,266.5542	$1,266.55	$1,266.60	$1,266.50