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	$53.41	6.277%	$56.7625	$56.76	$56.75	$56.80
Purchase #2	$13.88	9.679%	$15.2234	$15.22	$15.20	$15.20
Purchase #3	$81.74	10.629%	$90.4281	$90.43	$90.45	$90.40
Purchase #4	$164.69	4.694%	$172.4205	$172.42	$172.40	$172.40
Purchase #5	$128.85	10.674%	$142.6034	$142.60	$142.60	$142.60
Purchase #6	$116.54	7.372%	$125.1313	$125.13	$125.15	$125.10
Purchase #7	$237.99	12.771%	$268.3837	$268.38	$268.40	$268.40
7 purchase totals =	$797.10		$870.9529	$870.94	$870.95	$870.90