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	$111.95	4.280%	$116.7415	$116.74	$116.75	$116.70
Purchase #2	$146.95	9.178%	$160.4371	$160.44	$160.45	$160.40
Purchase #3	$86.65	4.685%	$90.7096	$90.71	$90.70	$90.70
Purchase #4	$115.29	10.376%	$127.2525	$127.25	$127.25	$127.30
Purchase #5	$162.50	10.201%	$179.0766	$179.08	$179.10	$179.10
Purchase #6	$187.29	12.437%	$210.5833	$210.58	$210.60	$210.60
Purchase #7	$64.38	7.189%	$69.0083	$69.01	$69.00	$69.00
7 purchase totals =	$875.01		$953.8089	$953.81	$953.85	$953.80