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	$199.28	10.183%	$219.5727	$219.57	$219.55	$219.60
Purchase #2	$55.34	11.716%	$61.8236	$61.82	$61.80	$61.80
Purchase #3	$144.69	5.246%	$152.2804	$152.28	$152.30	$152.30
Purchase #4	$42.35	10.585%	$46.8327	$46.83	$46.85	$46.80
Purchase #5	$205.84	4.855%	$215.8335	$215.83	$215.85	$215.80
Purchase #6	$42.83	7.491%	$46.0384	$46.04	$46.05	$46.00
Purchase #7	$83.91	12.769%	$94.6245	$94.62	$94.60	$94.60
7 purchase totals =	$774.24		$837.0058	$836.99	$837.00	$836.90