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	$54.31	4.217%	$56.6003	$56.60	$56.60	$56.60
Purchase #2	$18.78	13.190%	$21.2571	$21.26	$21.25	$21.30
Purchase #3	$196.36	9.241%	$214.5056	$214.51	$214.50	$214.50
Purchase #4	$89.38	8.274%	$96.7753	$96.78	$96.80	$96.80
Purchase #5	$132.76	5.714%	$140.3459	$140.35	$140.35	$140.30
Purchase #6	$223.71	9.458%	$244.8685	$244.87	$244.85	$244.90
Purchase #7	$86.47	5.756%	$91.4472	$91.45	$91.45	$91.40
7 purchase totals =	$801.77		$865.7999	$865.82	$865.80	$865.80