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	$176.36	12.462%	$198.338	$198.34	$198.35	$198.30
Purchase #2	$250.29	3.189%	$258.2717	$258.27	$258.25	$258.30
Purchase #3	$236.78	9.697%	$259.7406	$259.74	$259.75	$259.70
Purchase #4	$136.92	9.849%	$150.4053	$150.41	$150.40	$150.40
Purchase #5	$121.88	4.222%	$127.0258	$127.03	$127.05	$127.00
Purchase #6	$143.28	13.142%	$162.1099	$162.11	$162.10	$162.10
Purchase #7	$29.85	12.820%	$33.6768	$33.68	$33.70	$33.70
7 purchase totals =	$1,095.36		$1,189.5681	$1,189.58	$1,189.60	$1,189.50