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	$234.51	11.116%	$260.5781	$260.58	$260.60	$260.60
Purchase #2	$17.38	5.111%	$18.2683	$18.27	$18.25	$18.30
Purchase #3	$168.66	9.854%	$185.2798	$185.28	$185.30	$185.30
Purchase #4	$210.30	13.301%	$238.272	$238.27	$238.25	$238.30
Purchase #5	$108.66	7.394%	$116.6943	$116.69	$116.70	$116.70
Purchase #6	$33.80	9.781%	$37.106	$37.11	$37.10	$37.10
Purchase #7	$229.39	10.150%	$252.6731	$252.67	$252.65	$252.70
7 purchase totals =	$1,002.70		$1,108.8716	$1,108.87	$1,108.85	$1,109.00