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	$229.78	7.277%	$246.5011	$246.50	$246.50	$246.50
Purchase #2	$20.92	3.138%	$21.5765	$21.58	$21.60	$21.60
Purchase #3	$60.37	11.682%	$67.4224	$67.42	$67.40	$67.40
Purchase #4	$155.84	5.329%	$164.1447	$164.14	$164.15	$164.10
Purchase #5	$95.63	11.451%	$106.5806	$106.58	$106.60	$106.60
Purchase #6	$77.47	11.767%	$86.5859	$86.59	$86.60	$86.60
Purchase #7	$61.82	9.348%	$67.5989	$67.60	$67.60	$67.60
7 purchase totals =	$701.83		$760.4101	$760.41	$760.45	$760.40