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	$233.67	3.631%	$242.1546	$242.15	$242.15	$242.20
Purchase #2	$114.44	11.438%	$127.5296	$127.53	$127.55	$127.50
Purchase #3	$236.83	7.453%	$254.4809	$254.48	$254.50	$254.50
Purchase #4	$60.32	10.123%	$66.4262	$66.43	$66.45	$66.40
Purchase #5	$100.67	9.762%	$110.4974	$110.50	$110.50	$110.50
Purchase #6	$77.55	7.414%	$83.2996	$83.30	$83.30	$83.30
Purchase #7	$127.94	12.211%	$143.5628	$143.56	$143.55	$143.60
7 purchase totals =	$951.42		$1,027.9511	$1,027.95	$1,028.00	$1,028.00