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	$243.63	6.606%	$259.7242	$259.72	$259.70	$259.70
Purchase #2	$141.84	7.746%	$152.8269	$152.83	$152.85	$152.80
Purchase #3	$225.61	13.228%	$255.4537	$255.45	$255.45	$255.50
Purchase #4	$106.97	10.323%	$118.0125	$118.01	$118.00	$118.00
Purchase #5	$247.67	10.493%	$273.658	$273.66	$273.65	$273.70
Purchase #6	$48.54	7.342%	$52.1038	$52.10	$52.10	$52.10
Purchase #7	$175.43	8.506%	$190.3521	$190.35	$190.35	$190.40
7 purchase totals =	$1,189.69		$1,302.1312	$1,302.12	$1,302.10	$1,302.20