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	$69.60	4.566%	$72.7779	$72.78	$72.80	$72.80
Purchase #2	$29.98	3.294%	$30.9675	$30.97	$30.95	$31.00
Purchase #3	$5.54	11.473%	$6.1756	$6.18	$6.20	$6.20
Purchase #4	$102.57	11.780%	$114.6527	$114.65	$114.65	$114.70
Purchase #5	$136.95	6.722%	$146.1558	$146.16	$146.15	$146.20
Purchase #6	$54.82	12.436%	$61.6374	$61.64	$61.65	$61.60
Purchase #7	$95.77	5.114%	$100.6677	$100.67	$100.65	$100.70
7 purchase totals =	$495.23		$533.0346	$533.05	$533.05	$533.20