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	$139.77	13.301%	$158.3608	$158.36	$158.35	$158.40
Purchase #2	$244.94	4.801%	$256.6996	$256.70	$256.70	$256.70
Purchase #3	$56.49	8.467%	$61.273	$61.27	$61.25	$61.30
Purchase #4	$189.51	12.485%	$213.1703	$213.17	$213.15	$213.20
Purchase #5	$157.96	9.395%	$172.8003	$172.80	$172.80	$172.80
Purchase #6	$67.62	5.444%	$71.3012	$71.30	$71.30	$71.30
Purchase #7	$155.82	13.852%	$177.4042	$177.40	$177.40	$177.40
7 purchase totals =	$1,012.11		$1,111.0094	$1,111.00	$1,110.95	$1,111.10