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	$46.59	5.599%	$49.1986	$49.20	$49.20	$49.20
Purchase #2	$126.88	12.800%	$143.1206	$143.12	$143.10	$143.10
Purchase #3	$211.66	5.432%	$223.1574	$223.16	$223.15	$223.20
Purchase #4	$37.62	3.480%	$38.9292	$38.93	$38.95	$38.90
Purchase #5	$101.84	9.567%	$111.583	$111.58	$111.60	$111.60
Purchase #6	$176.66	13.747%	$200.9455	$200.95	$200.95	$200.90
Purchase #7	$101.80	7.220%	$109.15	$109.15	$109.15	$109.20
7 purchase totals =	$803.05		$876.0843	$876.09	$876.10	$876.10