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	$29.88	10.558%	$33.0347	$33.03	$33.05	$33.00
Purchase #2	$146.49	3.871%	$152.1606	$152.16	$152.15	$152.20
Purchase #3	$105.33	6.175%	$111.8341	$111.83	$111.85	$111.80
Purchase #4	$175.71	12.520%	$197.7089	$197.71	$197.70	$197.70
Purchase #5	$235.91	13.439%	$267.6139	$267.61	$267.60	$267.60
Purchase #6	$86.72	9.521%	$94.9766	$94.98	$95.00	$95.00
Purchase #7	$165.38	5.112%	$173.8342	$173.83	$173.85	$173.80
7 purchase totals =	$945.42		$1,031.1630	$1,031.15	$1,031.20	$1,031.10