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	$130.29	10.117%	$143.4714	$143.47	$143.45	$143.50
Purchase #2	$47.85	11.736%	$53.4657	$53.47	$53.45	$53.50
Purchase #3	$167.75	5.466%	$176.9192	$176.92	$176.90	$176.90
Purchase #4	$55.64	5.793%	$58.8632	$58.86	$58.85	$58.90
Purchase #5	$136.87	10.257%	$150.9088	$150.91	$150.90	$150.90
Purchase #6	$235.51	9.558%	$258.02	$258.02	$258.00	$258.00
Purchase #7	$28.31	13.308%	$32.0775	$32.08	$32.10	$32.10
7 purchase totals =	$802.22		$873.7258	$873.73	$873.65	$873.80