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	$198.48	8.551%	$215.452	$215.45	$215.45	$215.50
Purchase #2	$33.71	11.475%	$37.5782	$37.58	$37.60	$37.60
Purchase #3	$51.88	8.423%	$56.2499	$56.25	$56.25	$56.20
Purchase #4	$85.89	9.237%	$93.8237	$93.82	$93.80	$93.80
Purchase #5	$67.84	7.847%	$73.1634	$73.16	$73.15	$73.20
Purchase #6	$144.32	13.705%	$164.0991	$164.10	$164.10	$164.10
Purchase #7	$46.84	3.596%	$48.5244	$48.52	$48.50	$48.50
7 purchase totals =	$628.96		$688.8907	$688.88	$688.85	$688.90