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	$206.34	7.769%	$222.3706	$222.37	$222.35	$222.40
Purchase #2	$155.36	10.773%	$172.0969	$172.10	$172.10	$172.10
Purchase #3	$151.76	9.680%	$166.4504	$166.45	$166.45	$166.50
Purchase #4	$208.81	6.291%	$221.9462	$221.95	$221.95	$221.90
Purchase #5	$101.89	13.389%	$115.5321	$115.53	$115.55	$115.50
Purchase #6	$230.60	6.744%	$246.1517	$246.15	$246.15	$246.20
Purchase #7	$18.59	9.578%	$20.3706	$20.37	$20.35	$20.40
7 purchase totals =	$1,073.35		$1,164.9185	$1,164.92	$1,164.90	$1,165.00