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	$127.25	7.501%	$136.795	$136.80	$136.80	$136.80
Purchase #2	$49.30	6.643%	$52.575	$52.58	$52.60	$52.60
Purchase #3	$54.28	5.688%	$57.3674	$57.37	$57.35	$57.40
Purchase #4	$153.47	8.411%	$166.3784	$166.38	$166.40	$166.40
Purchase #5	$61.61	3.693%	$63.8853	$63.89	$63.90	$63.90
Purchase #6	$95.78	10.406%	$105.7469	$105.75	$105.75	$105.70
Purchase #7	$131.72	10.809%	$145.9576	$145.96	$145.95	$146.00
7 purchase totals =	$673.41		$728.7056	$728.73	$728.75	$728.80