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	$208.44	10.359%	$230.0323	$230.03	$230.05	$230.00
Purchase #2	$139.96	4.187%	$145.8201	$145.82	$145.80	$145.80
Purchase #3	$151.25	3.226%	$156.1293	$156.13	$156.15	$156.10
Purchase #4	$243.56	4.197%	$253.7822	$253.78	$253.80	$253.80
Purchase #5	$38.65	4.691%	$40.4631	$40.46	$40.45	$40.50
Purchase #6	$211.39	5.570%	$223.1644	$223.16	$223.15	$223.20
Purchase #7	$39.72	10.365%	$43.837	$43.84	$43.85	$43.80
7 purchase totals =	$1,032.97		$1,093.2284	$1,093.22	$1,093.25	$1,093.20