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	$21.77	10.412%	$24.0367	$24.04	$24.05	$24.00
Purchase #2	$52.71	12.483%	$59.2898	$59.29	$59.30	$59.30
Purchase #3	$183.89	8.590%	$199.6862	$199.69	$199.70	$199.70
Purchase #4	$209.75	10.581%	$231.9436	$231.94	$231.95	$231.90
Purchase #5	$188.55	7.393%	$202.4895	$202.49	$202.50	$202.50
Purchase #6	$48.60	8.389%	$52.6771	$52.68	$52.70	$52.70
Purchase #7	$242.34	5.320%	$255.2325	$255.23	$255.25	$255.20
7 purchase totals =	$947.61		$1,025.3554	$1,025.36	$1,025.45	$1,025.30