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	$167.78	11.805%	$187.5864	$187.59	$187.60	$187.60
Purchase #2	$118.37	4.545%	$123.7499	$123.75	$123.75	$123.70
Purchase #3	$213.52	6.647%	$227.7127	$227.71	$227.70	$227.70
Purchase #4	$206.58	8.275%	$223.6745	$223.67	$223.65	$223.70
Purchase #5	$222.99	3.328%	$230.4111	$230.41	$230.40	$230.40
Purchase #6	$34.28	7.407%	$36.8191	$36.82	$36.80	$36.80
Purchase #7	$45.75	12.661%	$51.5424	$51.54	$51.55	$51.50
7 purchase totals =	$1,009.27		$1,081.4961	$1,081.49	$1,081.45	$1,081.40