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	$65.57	10.559%	$72.4935	$72.49	$72.50	$72.50
Purchase #2	$155.86	5.338%	$164.1798	$164.18	$164.20	$164.20
Purchase #3	$115.55	9.810%	$126.8855	$126.89	$126.90	$126.90
Purchase #4	$136.63	8.533%	$148.2886	$148.29	$148.30	$148.30
Purchase #5	$18.59	4.472%	$19.4213	$19.42	$19.40	$19.40
Purchase #6	$183.63	4.709%	$192.2771	$192.28	$192.30	$192.30
Purchase #7	$204.94	11.443%	$228.3913	$228.39	$228.40	$228.40
7 purchase totals =	$880.77		$951.9371	$951.94	$952.00	$952.00