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	$72.49	4.643%	$75.8557	$75.86	$75.85	$75.90
Purchase #2	$140.64	7.705%	$151.4763	$151.48	$151.50	$151.50
Purchase #3	$93.52	7.297%	$100.3442	$100.34	$100.35	$100.30
Purchase #4	$108.81	3.825%	$112.972	$112.97	$112.95	$113.00
Purchase #5	$233.83	11.138%	$259.874	$259.87	$259.85	$259.90
Purchase #6	$134.29	13.729%	$152.7267	$152.73	$152.75	$152.70
Purchase #7	$30.65	7.388%	$32.9144	$32.91	$32.90	$32.90
7 purchase totals =	$814.23		$886.1633	$886.16	$886.15	$886.20