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	$164.96	8.440%	$178.8826	$178.88	$178.90	$178.90
Purchase #2	$177.94	11.819%	$198.9707	$198.97	$198.95	$199.00
Purchase #3	$243.38	11.111%	$270.422	$270.42	$270.40	$270.40
Purchase #4	$29.87	10.218%	$32.9221	$32.92	$32.90	$32.90
Purchase #5	$77.94	13.766%	$88.6692	$88.67	$88.65	$88.70
Purchase #6	$191.25	7.227%	$205.0716	$205.07	$205.05	$205.10
Purchase #7	$105.97	5.500%	$111.7984	$111.80	$111.80	$111.80
7 purchase totals =	$991.31		$1,086.7366	$1,086.73	$1,086.65	$1,086.80