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	$20.57	6.633%	$21.9344	$21.93	$21.95	$21.90
Purchase #2	$244.78	7.327%	$262.715	$262.72	$262.70	$262.70
Purchase #3	$128.59	7.368%	$138.0645	$138.06	$138.05	$138.10
Purchase #4	$198.81	9.542%	$217.7805	$217.78	$217.80	$217.80
Purchase #5	$99.98	4.740%	$104.7191	$104.72	$104.70	$104.70
Purchase #6	$225.89	8.661%	$245.4543	$245.45	$245.45	$245.50
Purchase #7	$151.77	6.857%	$162.1769	$162.18	$162.20	$162.20
7 purchase totals =	$1,070.39		$1,152.8447	$1,152.84	$1,152.85	$1,152.90