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	$32.68	4.346%	$34.1003	$34.10	$34.10	$34.10
Purchase #2	$63.48	6.366%	$67.5211	$67.52	$67.50	$67.50
Purchase #3	$149.40	8.837%	$162.6025	$162.60	$162.60	$162.60
Purchase #4	$67.57	13.261%	$76.5305	$76.53	$76.55	$76.50
Purchase #5	$31.79	13.474%	$36.0734	$36.07	$36.05	$36.10
Purchase #6	$138.76	9.427%	$151.8409	$151.84	$151.85	$151.80
Purchase #7	$208.77	6.745%	$222.8515	$222.85	$222.85	$222.90
7 purchase totals =	$692.45		$751.5202	$751.51	$751.50	$751.50