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	$160.82	9.301%	$175.7779	$175.78	$175.80	$175.80
Purchase #2	$57.81	5.258%	$60.8496	$60.85	$60.85	$60.80
Purchase #3	$146.93	12.808%	$165.7488	$165.75	$165.75	$165.70
Purchase #4	$92.31	3.466%	$95.5095	$95.51	$95.50	$95.50
Purchase #5	$29.34	12.153%	$32.9057	$32.91	$32.90	$32.90
Purchase #6	$231.84	4.605%	$242.5162	$242.52	$242.50	$242.50
Purchase #7	$238.37	6.846%	$254.6888	$254.69	$254.70	$254.70
7 purchase totals =	$957.42		$1,027.9965	$1,028.01	$1,028.00	$1,027.90