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	$247.26	8.143%	$267.3944	$267.39	$267.40	$267.40
Purchase #2	$52.77	7.246%	$56.5937	$56.59	$56.60	$56.60
Purchase #3	$92.42	5.497%	$97.5003	$97.50	$97.50	$97.50
Purchase #4	$95.40	8.282%	$103.301	$103.30	$103.30	$103.30
Purchase #5	$209.34	6.105%	$222.1202	$222.12	$222.10	$222.10
Purchase #6	$63.68	3.417%	$65.8559	$65.86	$65.85	$65.90
Purchase #7	$52.48	11.648%	$58.5929	$58.59	$58.60	$58.60
7 purchase totals =	$813.35		$871.3584	$871.35	$871.35	$871.40