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	$236.37	13.176%	$267.5141	$267.51	$267.50	$267.50
Purchase #2	$49.68	11.793%	$55.5388	$55.54	$55.55	$55.50
Purchase #3	$109.72	4.791%	$114.9767	$114.98	$115.00	$115.00
Purchase #4	$97.32	8.396%	$105.491	$105.49	$105.50	$105.50
Purchase #5	$74.39	11.684%	$83.0817	$83.08	$83.10	$83.10
Purchase #6	$130.58	8.409%	$141.5605	$141.56	$141.55	$141.60
Purchase #7	$178.34	11.672%	$199.1558	$199.16	$199.15	$199.20
7 purchase totals =	$876.40		$967.3186	$967.32	$967.35	$967.40