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	$20.74	9.837%	$22.7802	$22.78	$22.80	$22.80
Purchase #2	$116.64	9.252%	$127.4315	$127.43	$127.45	$127.40
Purchase #3	$90.83	4.473%	$94.8928	$94.89	$94.90	$94.90
Purchase #4	$75.80	6.255%	$80.5413	$80.54	$80.55	$80.50
Purchase #5	$204.56	6.388%	$217.6273	$217.63	$217.65	$217.60
Purchase #6	$132.63	13.615%	$150.6876	$150.69	$150.70	$150.70
Purchase #7	$28.58	12.179%	$32.0608	$32.06	$32.05	$32.10
7 purchase totals =	$669.78		$726.0215	$726.02	$726.10	$726.00