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	$22.98	10.795%	$25.4607	$25.46	$25.45	$25.50
Purchase #2	$162.59	10.164%	$179.1156	$179.12	$179.10	$179.10
Purchase #3	$99.42	7.856%	$107.2304	$107.23	$107.25	$107.20
Purchase #4	$134.36	3.827%	$139.502	$139.50	$139.50	$139.50
Purchase #5	$205.59	13.349%	$233.0342	$233.03	$233.05	$233.00
Purchase #6	$184.71	13.152%	$209.0031	$209.00	$209.00	$209.00
Purchase #7	$119.99	5.429%	$126.5043	$126.50	$126.50	$126.50
7 purchase totals =	$929.64		$1,019.8503	$1,019.84	$1,019.85	$1,019.80