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	$23.94	6.365%	$25.4638	$25.46	$25.45	$25.50
Purchase #2	$190.48	10.404%	$210.2975	$210.30	$210.30	$210.30
Purchase #3	$90.99	3.434%	$94.1146	$94.11	$94.10	$94.10
Purchase #4	$155.25	11.164%	$172.5821	$172.58	$172.60	$172.60
Purchase #5	$108.49	7.610%	$116.7461	$116.75	$116.75	$116.70
Purchase #6	$222.50	8.124%	$240.5759	$240.58	$240.60	$240.60
Purchase #7	$100.88	4.692%	$105.6133	$105.61	$105.60	$105.60
7 purchase totals =	$892.53		$965.3933	$965.39	$965.40	$965.40