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	$151.29	9.229%	$165.2526	$165.25	$165.25	$165.30
Purchase #2	$130.37	10.420%	$143.9546	$143.95	$143.95	$144.00
Purchase #3	$174.36	8.105%	$188.4919	$188.49	$188.50	$188.50
Purchase #4	$52.73	13.180%	$59.6798	$59.68	$59.70	$59.70
Purchase #5	$166.49	11.392%	$185.4565	$185.46	$185.45	$185.50
Purchase #6	$175.58	4.640%	$183.7269	$183.73	$183.75	$183.70
Purchase #7	$92.60	4.448%	$96.7188	$96.72	$96.70	$96.70
7 purchase totals =	$943.42		$1,023.2811	$1,023.28	$1,023.30	$1,023.40