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	$179.79	11.382%	$200.2537	$200.25	$200.25	$200.30
Purchase #2	$152.25	9.228%	$166.2996	$166.30	$166.30	$166.30
Purchase #3	$173.25	4.291%	$180.6842	$180.68	$180.70	$180.70
Purchase #4	$220.50	13.505%	$250.2785	$250.28	$250.30	$250.30
Purchase #5	$141.73	6.243%	$150.5782	$150.58	$150.60	$150.60
Purchase #6	$19.43	7.187%	$20.8264	$20.83	$20.85	$20.80
Purchase #7	$54.80	10.310%	$60.4499	$60.45	$60.45	$60.40
7 purchase totals =	$941.75		$1,029.3705	$1,029.37	$1,029.45	$1,029.40