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	$49.43	8.175%	$53.4709	$53.47	$53.45	$53.50
Purchase #2	$32.78	6.704%	$34.9776	$34.98	$35.00	$35.00
Purchase #3	$175.59	11.429%	$195.6582	$195.66	$195.65	$195.70
Purchase #4	$144.74	13.675%	$164.5332	$164.53	$164.55	$164.50
Purchase #5	$232.25	10.459%	$256.541	$256.54	$256.55	$256.50
Purchase #6	$34.89	10.153%	$38.4324	$38.43	$38.45	$38.40
Purchase #7	$111.30	3.722%	$115.4426	$115.44	$115.45	$115.40
7 purchase totals =	$780.98		$859.0559	$859.05	$859.10	$859.00