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	$172.35	4.219%	$179.6214	$179.62	$179.60	$179.60
Purchase #2	$209.83	3.477%	$217.1258	$217.13	$217.15	$217.10
Purchase #3	$180.80	4.141%	$188.2869	$188.29	$188.30	$188.30
Purchase #4	$169.66	5.118%	$178.3432	$178.34	$178.35	$178.30
Purchase #5	$95.71	7.431%	$102.8222	$102.82	$102.80	$102.80
Purchase #6	$101.37	10.665%	$112.1811	$112.18	$112.20	$112.20
Purchase #7	$89.69	3.333%	$92.6794	$92.68	$92.70	$92.70
7 purchase totals =	$1,019.41		$1,071.0600	$1,071.06	$1,071.10	$1,071.00