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	$106.93	8.232%	$115.7325	$115.73	$115.75	$115.70
Purchase #2	$28.52	3.518%	$29.5233	$29.52	$29.50	$29.50
Purchase #3	$96.84	3.500%	$100.2294	$100.23	$100.25	$100.20
Purchase #4	$28.39	3.719%	$29.4458	$29.45	$29.45	$29.40
Purchase #5	$129.49	11.711%	$144.6546	$144.65	$144.65	$144.70
Purchase #6	$96.38	4.618%	$100.8308	$100.83	$100.85	$100.80
Purchase #7	$69.26	4.134%	$72.1232	$72.12	$72.10	$72.10
7 purchase totals =	$555.81		$592.5396	$592.53	$592.55	$592.40