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	$194.72	13.530%	$221.0656	$221.07	$221.05	$221.10
Purchase #2	$69.87	3.305%	$72.1792	$72.18	$72.20	$72.20
Purchase #3	$116.45	6.383%	$123.883	$123.88	$123.90	$123.90
Purchase #4	$97.42	5.709%	$102.9817	$102.98	$103.00	$103.00
Purchase #5	$230.81	4.264%	$240.6517	$240.65	$240.65	$240.70
Purchase #6	$43.47	4.382%	$45.3749	$45.37	$45.35	$45.40
Purchase #7	$10.41	4.689%	$10.8981	$10.90	$10.90	$10.90
7 purchase totals =	$763.15		$817.0342	$817.03	$817.05	$817.20