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	$152.54	12.866%	$172.1658	$172.17	$172.15	$172.20
Purchase #2	$145.89	4.677%	$152.7133	$152.71	$152.70	$152.70
Purchase #3	$111.46	9.112%	$121.6162	$121.62	$121.60	$121.60
Purchase #4	$128.37	4.130%	$133.6717	$133.67	$133.65	$133.70
Purchase #5	$72.66	8.106%	$78.5498	$78.55	$78.55	$78.50
Purchase #6	$244.35	7.299%	$262.1851	$262.19	$262.20	$262.20
Purchase #7	$134.41	5.316%	$141.5552	$141.56	$141.55	$141.60
7 purchase totals =	$989.68		$1,062.4571	$1,062.47	$1,062.40	$1,062.50