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	$137.93	12.831%	$155.6278	$155.63	$155.65	$155.60
Purchase #2	$97.68	11.841%	$109.2463	$109.25	$109.25	$109.20
Purchase #3	$225.59	8.392%	$244.5215	$244.52	$244.50	$244.50
Purchase #4	$29.96	7.106%	$32.089	$32.09	$32.10	$32.10
Purchase #5	$137.37	7.279%	$147.3692	$147.37	$147.35	$147.40
Purchase #6	$72.82	5.212%	$76.6154	$76.62	$76.60	$76.60
Purchase #7	$173.75	3.631%	$180.0589	$180.06	$180.05	$180.10
7 purchase totals =	$875.10		$945.5281	$945.54	$945.50	$945.50