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	$105.40	5.391%	$111.0821	$111.08	$111.10	$111.10
Purchase #2	$67.79	13.260%	$76.779	$76.78	$76.80	$76.80
Purchase #3	$35.64	13.372%	$40.4058	$40.41	$40.40	$40.40
Purchase #4	$146.31	12.491%	$164.5856	$164.59	$164.60	$164.60
Purchase #5	$153.84	12.591%	$173.21	$173.21	$173.20	$173.20
Purchase #6	$202.50	7.136%	$216.9504	$216.95	$216.95	$217.00
Purchase #7	$48.61	12.652%	$54.7601	$54.76	$54.75	$54.80
7 purchase totals =	$760.09		$837.7730	$837.78	$837.80	$837.90