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	$198.44	4.247%	$206.8677	$206.87	$206.85	$206.90
Purchase #2	$5.66	13.403%	$6.4186	$6.42	$6.40	$6.40
Purchase #3	$34.82	8.593%	$37.8121	$37.81	$37.80	$37.80
Purchase #4	$127.31	7.237%	$136.5234	$136.52	$136.50	$136.50
Purchase #5	$56.45	5.543%	$59.579	$59.58	$59.60	$59.60
Purchase #6	$47.26	8.593%	$51.3211	$51.32	$51.30	$51.30
Purchase #7	$92.54	10.623%	$102.3705	$102.37	$102.35	$102.40
7 purchase totals =	$562.48		$600.8924	$600.89	$600.80	$600.90