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	$211.86	3.553%	$219.3874	$219.39	$219.40	$219.40
Purchase #2	$233.37	3.724%	$242.0607	$242.06	$242.05	$242.10
Purchase #3	$220.44	4.337%	$230.0005	$230.00	$230.00	$230.00
Purchase #4	$108.85	13.527%	$123.5741	$123.57	$123.55	$123.60
Purchase #5	$43.58	3.168%	$44.9606	$44.96	$44.95	$45.00
Purchase #6	$38.38	7.128%	$41.1157	$41.12	$41.10	$41.10
Purchase #7	$151.33	12.272%	$169.9012	$169.90	$169.90	$169.90
7 purchase totals =	$1,007.81		$1,071.0002	$1,071.00	$1,070.95	$1,071.10