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	$54.32	11.575%	$60.6075	$60.61	$60.60	$60.60
Purchase #2	$102.78	6.861%	$109.8317	$109.83	$109.85	$109.80
Purchase #3	$196.56	13.130%	$222.3683	$222.37	$222.35	$222.40
Purchase #4	$14.93	9.448%	$16.3406	$16.34	$16.35	$16.30
Purchase #5	$151.54	7.391%	$162.7403	$162.74	$162.75	$162.70
Purchase #6	$166.31	12.599%	$187.2634	$187.26	$187.25	$187.30
Purchase #7	$118.29	10.320%	$130.4975	$130.50	$130.50	$130.50
7 purchase totals =	$804.73		$889.6493	$889.65	$889.65	$889.60