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	$67.51	4.574%	$70.5979	$70.60	$70.60	$70.60
Purchase #2	$233.66	12.259%	$262.3044	$262.30	$262.30	$262.30
Purchase #3	$42.52	13.249%	$48.1535	$48.15	$48.15	$48.20
Purchase #4	$16.40	12.331%	$18.4223	$18.42	$18.40	$18.40
Purchase #5	$20.37	5.102%	$21.4093	$21.41	$21.40	$21.40
Purchase #6	$96.42	9.811%	$105.8798	$105.88	$105.90	$105.90
Purchase #7	$176.35	11.155%	$196.0218	$196.02	$196.00	$196.00
7 purchase totals =	$653.23		$722.7890	$722.78	$722.75	$722.80