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	$79.47	7.563%	$85.4803	$85.48	$85.50	$85.50
Purchase #2	$194.25	13.558%	$220.5864	$220.59	$220.60	$220.60
Purchase #3	$128.98	6.869%	$137.8396	$137.84	$137.85	$137.80
Purchase #4	$13.26	7.710%	$14.2823	$14.28	$14.30	$14.30
Purchase #5	$25.47	5.273%	$26.813	$26.81	$26.80	$26.80
Purchase #6	$142.48	6.154%	$151.2482	$151.25	$151.25	$151.20
Purchase #7	$112.31	13.536%	$127.5123	$127.51	$127.50	$127.50
7 purchase totals =	$696.22		$763.7621	$763.76	$763.80	$763.70