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	$177.52	11.603%	$198.1176	$198.12	$198.10	$198.10
Purchase #2	$96.72	8.539%	$104.9789	$104.98	$105.00	$105.00
Purchase #3	$67.69	6.240%	$71.9139	$71.91	$71.90	$71.90
Purchase #4	$129.81	5.249%	$136.6237	$136.62	$136.60	$136.60
Purchase #5	$103.39	11.675%	$115.4608	$115.46	$115.45	$115.50
Purchase #6	$234.55	10.115%	$258.2747	$258.27	$258.25	$258.30
Purchase #7	$213.30	6.106%	$226.3241	$226.32	$226.30	$226.30
7 purchase totals =	$1,022.98		$1,111.6937	$1,111.68	$1,111.60	$1,111.70