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	$60.31	4.322%	$62.9166	$62.92	$62.90	$62.90
Purchase #2	$175.60	7.527%	$188.8174	$188.82	$188.80	$188.80
Purchase #3	$58.67	5.709%	$62.0195	$62.02	$62.00	$62.00
Purchase #4	$42.56	5.332%	$44.8293	$44.83	$44.85	$44.80
Purchase #5	$246.34	13.499%	$279.5934	$279.59	$279.60	$279.60
Purchase #6	$155.27	10.338%	$171.3218	$171.32	$171.30	$171.30
Purchase #7	$141.81	8.611%	$154.0213	$154.02	$154.00	$154.00
7 purchase totals =	$880.56		$963.5193	$963.52	$963.45	$963.40