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	$91.83	10.341%	$101.3261	$101.33	$101.35	$101.30
Purchase #2	$111.51	10.813%	$123.5676	$123.57	$123.55	$123.60
Purchase #3	$231.57	4.841%	$242.7803	$242.78	$242.80	$242.80
Purchase #4	$16.64	4.548%	$17.3968	$17.40	$17.40	$17.40
Purchase #5	$184.33	11.589%	$205.692	$205.69	$205.70	$205.70
Purchase #6	$200.66	9.547%	$219.817	$219.82	$219.80	$219.80
Purchase #7	$100.39	8.478%	$108.9011	$108.90	$108.90	$108.90
7 purchase totals =	$936.93		$1,019.4809	$1,019.49	$1,019.50	$1,019.50