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	$212.57	4.616%	$222.3822	$222.38	$222.40	$222.40
Purchase #2	$216.98	3.577%	$224.7414	$224.74	$224.75	$224.70
Purchase #3	$211.90	8.692%	$230.3183	$230.32	$230.30	$230.30
Purchase #4	$87.51	3.159%	$90.2744	$90.27	$90.25	$90.30
Purchase #5	$27.52	8.751%	$29.9283	$29.93	$29.95	$29.90
Purchase #6	$92.36	7.716%	$99.4865	$99.49	$99.50	$99.50
Purchase #7	$102.45	12.666%	$115.4263	$115.43	$115.45	$115.40
7 purchase totals =	$951.29		$1,012.5574	$1,012.56	$1,012.60	$1,012.50