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	$61.64	9.704%	$67.6215	$67.62	$67.60	$67.60
Purchase #2	$100.32	13.529%	$113.8923	$113.89	$113.90	$113.90
Purchase #3	$37.47	10.615%	$41.4474	$41.45	$41.45	$41.40
Purchase #4	$60.40	11.695%	$67.4638	$67.46	$67.45	$67.50
Purchase #5	$218.56	12.874%	$246.6974	$246.70	$246.70	$246.70
Purchase #6	$40.92	3.130%	$42.2008	$42.20	$42.20	$42.20
Purchase #7	$230.40	4.493%	$240.7519	$240.75	$240.75	$240.80
7 purchase totals =	$749.71		$820.0751	$820.07	$820.05	$820.10