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	$228.91	6.795%	$244.4644	$244.46	$244.45	$244.50
Purchase #2	$244.72	3.868%	$254.1858	$254.19	$254.20	$254.20
Purchase #3	$238.51	11.595%	$266.1652	$266.17	$266.15	$266.20
Purchase #4	$25.84	13.353%	$29.2904	$29.29	$29.30	$29.30
Purchase #5	$140.90	11.198%	$156.678	$156.68	$156.70	$156.70
Purchase #6	$80.73	12.507%	$90.8269	$90.83	$90.85	$90.80
Purchase #7	$212.82	12.225%	$238.8372	$238.84	$238.85	$238.80
7 purchase totals =	$1,172.43		$1,280.4479	$1,280.46	$1,280.50	$1,280.50