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	$213.35	9.486%	$233.5884	$233.59	$233.60	$233.60
Purchase #2	$151.62	8.266%	$164.1529	$164.15	$164.15	$164.20
Purchase #3	$163.57	10.243%	$180.3245	$180.32	$180.30	$180.30
Purchase #4	$95.52	10.202%	$105.265	$105.27	$105.25	$105.30
Purchase #5	$89.57	12.601%	$100.8567	$100.86	$100.85	$100.90
Purchase #6	$91.56	10.587%	$101.2535	$101.25	$101.25	$101.30
Purchase #7	$121.65	3.808%	$126.2824	$126.28	$126.30	$126.30
7 purchase totals =	$926.84		$1,011.7234	$1,011.72	$1,011.70	$1,011.90