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	$157.83	4.280%	$164.5851	$164.59	$164.60	$164.60
Purchase #2	$52.94	6.865%	$56.5743	$56.57	$56.55	$56.60
Purchase #3	$180.78	13.784%	$205.6987	$205.70	$205.70	$205.70
Purchase #4	$242.63	10.576%	$268.2905	$268.29	$268.30	$268.30
Purchase #5	$97.53	3.208%	$100.6588	$100.66	$100.65	$100.70
Purchase #6	$108.80	6.660%	$116.0461	$116.05	$116.05	$116.00
Purchase #7	$135.52	10.117%	$149.2306	$149.23	$149.25	$149.20
7 purchase totals =	$976.03		$1,061.0841	$1,061.09	$1,061.10	$1,061.10