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	$229.65	11.180%	$255.3249	$255.32	$255.30	$255.30
Purchase #2	$174.57	5.444%	$184.0736	$184.07	$184.05	$184.10
Purchase #3	$13.94	9.860%	$15.3145	$15.31	$15.30	$15.30
Purchase #4	$87.27	3.793%	$90.5802	$90.58	$90.60	$90.60
Purchase #5	$209.27	5.170%	$220.0893	$220.09	$220.10	$220.10
Purchase #6	$20.61	4.712%	$21.5811	$21.58	$21.60	$21.60
Purchase #7	$210.59	10.468%	$232.6346	$232.63	$232.65	$232.60
7 purchase totals =	$945.90		$1,019.5982	$1,019.58	$1,019.60	$1,019.60