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	$230.52	11.434%	$256.8777	$256.88	$256.90	$256.90
Purchase #2	$192.83	11.651%	$215.2966	$215.30	$215.30	$215.30
Purchase #3	$177.66	7.217%	$190.4817	$190.48	$190.50	$190.50
Purchase #4	$24.53	6.676%	$26.1676	$26.17	$26.15	$26.20
Purchase #5	$158.63	6.483%	$168.914	$168.91	$168.90	$168.90
Purchase #6	$158.99	9.161%	$173.5551	$173.56	$173.55	$173.60
Purchase #7	$136.43	8.776%	$148.4031	$148.40	$148.40	$148.40
7 purchase totals =	$1,079.59		$1,179.6958	$1,179.70	$1,179.70	$1,179.80