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	$54.34	12.365%	$61.0591	$61.06	$61.05	$61.10
Purchase #2	$19.58	11.451%	$21.8221	$21.82	$21.80	$21.80
Purchase #3	$31.30	10.689%	$34.6457	$34.65	$34.65	$34.60
Purchase #4	$69.39	11.576%	$77.4226	$77.42	$77.40	$77.40
Purchase #5	$53.75	6.695%	$57.3486	$57.35	$57.35	$57.30
Purchase #6	$126.65	12.181%	$142.0772	$142.08	$142.10	$142.10
Purchase #7	$240.52	3.327%	$248.5221	$248.52	$248.50	$248.50
7 purchase totals =	$595.53		$642.8974	$642.90	$642.85	$642.80