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	$162.48	13.139%	$183.8282	$183.83	$183.85	$183.80
Purchase #2	$18.43	10.133%	$20.2975	$20.30	$20.30	$20.30
Purchase #3	$139.59	6.693%	$148.9328	$148.93	$148.95	$148.90
Purchase #4	$246.51	3.379%	$254.8396	$254.84	$254.85	$254.80
Purchase #5	$30.41	5.667%	$32.1333	$32.13	$32.15	$32.10
Purchase #6	$64.41	13.128%	$72.8657	$72.87	$72.85	$72.90
Purchase #7	$138.65	9.507%	$151.8315	$151.83	$151.85	$151.80
7 purchase totals =	$800.48		$864.7286	$864.73	$864.80	$864.60