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	$85.52	5.809%	$90.4879	$90.49	$90.50	$90.50
Purchase #2	$82.79	6.325%	$88.0265	$88.03	$88.05	$88.00
Purchase #3	$224.83	6.746%	$239.997	$240.00	$240.00	$240.00
Purchase #4	$144.38	8.235%	$156.2697	$156.27	$156.25	$156.30
Purchase #5	$81.30	4.668%	$85.0951	$85.10	$85.10	$85.10
Purchase #6	$217.77	11.429%	$242.6589	$242.66	$242.65	$242.70
Purchase #7	$142.95	7.295%	$153.3782	$153.38	$153.40	$153.40
7 purchase totals =	$979.54		$1,055.9133	$1,055.93	$1,055.95	$1,056.00