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	$159.35	8.675%	$173.1736	$173.17	$173.15	$173.20
Purchase #2	$55.79	3.173%	$57.5602	$57.56	$57.55	$57.60
Purchase #3	$202.31	6.246%	$214.9463	$214.95	$214.95	$214.90
Purchase #4	$150.69	11.186%	$167.5462	$167.55	$167.55	$167.50
Purchase #5	$175.82	5.730%	$185.8945	$185.89	$185.90	$185.90
Purchase #6	$226.95	11.435%	$252.9017	$252.90	$252.90	$252.90
Purchase #7	$55.66	3.410%	$57.558	$57.56	$57.55	$57.60
7 purchase totals =	$1,026.57		$1,109.5805	$1,109.58	$1,109.55	$1,109.60