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	$59.56	10.136%	$65.597	$65.60	$65.60	$65.60
Purchase #2	$58.91	8.488%	$63.9103	$63.91	$63.90	$63.90
Purchase #3	$223.89	9.345%	$244.8125	$244.81	$244.80	$244.80
Purchase #4	$164.97	11.503%	$183.9465	$183.95	$183.95	$183.90
Purchase #5	$132.32	7.816%	$142.6621	$142.66	$142.65	$142.70
Purchase #6	$127.26	9.441%	$139.2746	$139.27	$139.25	$139.30
Purchase #7	$143.55	10.820%	$159.0821	$159.08	$159.10	$159.10
7 purchase totals =	$910.46		$999.2851	$999.28	$999.25	$999.30