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	$116.94	12.598%	$131.6721	$131.67	$131.65	$131.70
Purchase #2	$157.86	5.142%	$165.9772	$165.98	$166.00	$166.00
Purchase #3	$234.59	9.249%	$256.2872	$256.29	$256.30	$256.30
Purchase #4	$22.65	9.329%	$24.763	$24.76	$24.75	$24.80
Purchase #5	$231.93	11.834%	$259.3766	$259.38	$259.40	$259.40
Purchase #6	$198.52	5.286%	$209.0138	$209.01	$209.00	$209.00
Purchase #7	$52.82	13.303%	$59.8466	$59.85	$59.85	$59.80
7 purchase totals =	$1,015.31		$1,106.9365	$1,106.94	$1,106.95	$1,107.00