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	$105.46	4.333%	$110.0296	$110.03	$110.05	$110.00
Purchase #2	$54.50	3.871%	$56.6097	$56.61	$56.60	$56.60
Purchase #3	$38.56	13.170%	$43.6384	$43.64	$43.65	$43.60
Purchase #4	$40.55	5.672%	$42.85	$42.85	$42.85	$42.90
Purchase #5	$158.31	13.503%	$179.6866	$179.69	$179.70	$179.70
Purchase #6	$57.30	5.456%	$60.4263	$60.43	$60.45	$60.40
Purchase #7	$46.50	9.803%	$51.0584	$51.06	$51.05	$51.10
7 purchase totals =	$501.18		$544.2990	$544.31	$544.35	$544.30