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	$178.34	11.838%	$199.4519	$199.45	$199.45	$199.50
Purchase #2	$14.30	3.650%	$14.822	$14.82	$14.80	$14.80
Purchase #3	$108.83	5.786%	$115.1269	$115.13	$115.15	$115.10
Purchase #4	$121.80	4.644%	$127.4564	$127.46	$127.45	$127.50
Purchase #5	$206.83	11.633%	$230.8905	$230.89	$230.90	$230.90
Purchase #6	$39.51	9.126%	$43.1157	$43.12	$43.10	$43.10
Purchase #7	$64.74	7.542%	$69.6227	$69.62	$69.60	$69.60
7 purchase totals =	$734.35		$800.4861	$800.49	$800.45	$800.50