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	$163.51	5.679%	$172.7957	$172.80	$172.80	$172.80
Purchase #2	$156.95	4.765%	$164.4287	$164.43	$164.45	$164.40
Purchase #3	$118.94	7.269%	$127.5857	$127.59	$127.60	$127.60
Purchase #4	$121.92	5.672%	$128.8353	$128.84	$128.85	$128.80
Purchase #5	$203.93	9.420%	$223.1402	$223.14	$223.15	$223.10
Purchase #6	$21.98	11.520%	$24.5121	$24.51	$24.50	$24.50
Purchase #7	$74.58	9.787%	$81.8791	$81.88	$81.90	$81.90
7 purchase totals =	$861.81		$923.1768	$923.19	$923.25	$923.10