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	$167.51	10.489%	$185.0801	$185.08	$185.10	$185.10
Purchase #2	$242.48	13.263%	$274.6401	$274.64	$274.65	$274.60
Purchase #3	$100.91	7.167%	$108.1422	$108.14	$108.15	$108.10
Purchase #4	$63.95	3.303%	$66.0623	$66.06	$66.05	$66.10
Purchase #5	$127.51	8.119%	$137.8625	$137.86	$137.85	$137.90
Purchase #6	$117.35	9.605%	$128.6215	$128.62	$128.60	$128.60
Purchase #7	$165.26	12.208%	$185.4349	$185.43	$185.45	$185.40
7 purchase totals =	$984.97		$1,085.8436	$1,085.83	$1,085.85	$1,085.80