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	$78.45	5.622%	$82.8605	$82.86	$82.85	$82.90
Purchase #2	$36.83	12.663%	$41.4938	$41.49	$41.50	$41.50
Purchase #3	$89.86	12.770%	$101.3351	$101.34	$101.35	$101.30
Purchase #4	$147.42	7.748%	$158.8421	$158.84	$158.85	$158.80
Purchase #5	$46.81	4.506%	$48.9193	$48.92	$48.90	$48.90
Purchase #6	$194.67	5.762%	$205.8869	$205.89	$205.90	$205.90
Purchase #7	$82.92	11.163%	$92.1764	$92.18	$92.20	$92.20
7 purchase totals =	$676.96		$731.5141	$731.52	$731.55	$731.50