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	$188.83	10.208%	$208.1058	$208.11	$208.10	$208.10
Purchase #2	$162.47	8.617%	$176.47	$176.47	$176.45	$176.50
Purchase #3	$137.69	10.187%	$151.7165	$151.72	$151.70	$151.70
Purchase #4	$217.55	10.404%	$240.1839	$240.18	$240.20	$240.20
Purchase #5	$208.94	8.123%	$225.9122	$225.91	$225.90	$225.90
Purchase #6	$240.98	5.871%	$255.1279	$255.13	$255.15	$255.10
Purchase #7	$190.41	4.313%	$198.6224	$198.62	$198.60	$198.60
7 purchase totals =	$1,346.87		$1,456.1387	$1,456.14	$1,456.10	$1,456.10