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	$51.59	9.198%	$56.3352	$56.34	$56.35	$56.30
Purchase #2	$20.78	3.507%	$21.5088	$21.51	$21.50	$21.50
Purchase #3	$100.62	8.844%	$109.5188	$109.52	$109.50	$109.50
Purchase #4	$88.65	12.278%	$99.5344	$99.53	$99.55	$99.50
Purchase #5	$239.51	9.539%	$262.3569	$262.36	$262.35	$262.40
Purchase #6	$16.74	8.485%	$18.1604	$18.16	$18.15	$18.20
Purchase #7	$113.40	12.482%	$127.5546	$127.55	$127.55	$127.60
7 purchase totals =	$631.29		$694.9691	$694.97	$694.95	$695.00