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	$103.45	10.673%	$114.4912	$114.49	$114.50	$114.50
Purchase #2	$176.58	6.222%	$187.5668	$187.57	$187.55	$187.60
Purchase #3	$105.56	4.163%	$109.9545	$109.95	$109.95	$110.00
Purchase #4	$165.95	10.835%	$183.9307	$183.93	$183.95	$183.90
Purchase #5	$112.76	3.619%	$116.8408	$116.84	$116.85	$116.80
Purchase #6	$57.84	5.709%	$61.1421	$61.14	$61.15	$61.10
Purchase #7	$19.93	8.308%	$21.5858	$21.59	$21.60	$21.60
7 purchase totals =	$742.07		$795.5119	$795.51	$795.55	$795.50