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	$154.93	5.747%	$163.8338	$163.83	$163.85	$163.80
Purchase #2	$174.82	6.354%	$185.9281	$185.93	$185.95	$185.90
Purchase #3	$114.78	13.285%	$130.0285	$130.03	$130.05	$130.00
Purchase #4	$100.42	11.357%	$111.8247	$111.82	$111.80	$111.80
Purchase #5	$44.50	7.176%	$47.6933	$47.69	$47.70	$47.70
Purchase #6	$172.51	9.820%	$189.4505	$189.45	$189.45	$189.50
Purchase #7	$62.28	8.740%	$67.7233	$67.72	$67.70	$67.70
7 purchase totals =	$824.24		$896.4822	$896.47	$896.50	$896.40