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	$178.89	10.785%	$198.1833	$198.18	$198.20	$198.20
Purchase #2	$92.92	11.600%	$103.6987	$103.70	$103.70	$103.70
Purchase #3	$89.70	12.450%	$100.8677	$100.87	$100.85	$100.90
Purchase #4	$16.43	11.651%	$18.3443	$18.34	$18.35	$18.30
Purchase #5	$206.38	5.619%	$217.9765	$217.98	$218.00	$218.00
Purchase #6	$66.75	8.516%	$72.4344	$72.43	$72.45	$72.40
Purchase #7	$211.76	11.482%	$236.0743	$236.07	$236.05	$236.10
7 purchase totals =	$862.83		$947.5792	$947.57	$947.60	$947.60