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	$95.47	3.204%	$98.5289	$98.53	$98.55	$98.50
Purchase #2	$49.54	5.173%	$52.1027	$52.10	$52.10	$52.10
Purchase #3	$247.52	4.548%	$258.7772	$258.78	$258.80	$258.80
Purchase #4	$242.89	13.539%	$275.7749	$275.77	$275.75	$275.80
Purchase #5	$218.57	10.498%	$241.5155	$241.52	$241.50	$241.50
Purchase #6	$233.83	9.584%	$256.2403	$256.24	$256.25	$256.20
Purchase #7	$162.92	8.118%	$176.1458	$176.15	$176.15	$176.10
7 purchase totals =	$1,250.74		$1,359.0853	$1,359.09	$1,359.10	$1,359.00