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	$104.33	11.673%	$116.5084	$116.51	$116.50	$116.50
Purchase #2	$78.29	10.859%	$86.7915	$86.79	$86.80	$86.80
Purchase #3	$106.64	5.388%	$112.3858	$112.39	$112.40	$112.40
Purchase #4	$164.50	10.224%	$181.3185	$181.32	$181.30	$181.30
Purchase #5	$61.81	13.700%	$70.278	$70.28	$70.30	$70.30
Purchase #6	$205.72	6.636%	$219.3716	$219.37	$219.35	$219.40
Purchase #7	$158.52	13.183%	$179.4177	$179.42	$179.40	$179.40
7 purchase totals =	$879.81		$966.0715	$966.08	$966.05	$966.10