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	$235.72	11.259%	$262.2597	$262.26	$262.25	$262.30
Purchase #2	$83.60	6.298%	$88.8651	$88.87	$88.85	$88.90
Purchase #3	$100.34	11.193%	$111.5711	$111.57	$111.55	$111.60
Purchase #4	$160.62	13.479%	$182.27	$182.27	$182.25	$182.30
Purchase #5	$127.60	10.852%	$141.4472	$141.45	$141.45	$141.40
Purchase #6	$20.35	5.646%	$21.499	$21.50	$21.50	$21.50
Purchase #7	$27.82	7.843%	$30.0019	$30.00	$30.00	$30.00
7 purchase totals =	$756.05		$837.9140	$837.92	$837.85	$838.00