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	$45.39	5.407%	$47.8442	$47.84	$47.85	$47.80
Purchase #2	$192.68	8.266%	$208.6069	$208.61	$208.60	$208.60
Purchase #3	$34.42	9.199%	$37.5863	$37.59	$37.60	$37.60
Purchase #4	$153.72	8.266%	$166.4265	$166.43	$166.45	$166.40
Purchase #5	$85.30	7.613%	$91.7939	$91.79	$91.80	$91.80
Purchase #6	$178.60	6.673%	$190.518	$190.52	$190.50	$190.50
Purchase #7	$86.49	7.326%	$92.8263	$92.83	$92.85	$92.80
7 purchase totals =	$776.60		$835.6021	$835.61	$835.65	$835.50