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	$170.31	12.771%	$192.0603	$192.06	$192.05	$192.10
Purchase #2	$116.57	5.659%	$123.1667	$123.17	$123.15	$123.20
Purchase #3	$95.95	8.230%	$103.8467	$103.85	$103.85	$103.80
Purchase #4	$105.66	11.729%	$118.0529	$118.05	$118.05	$118.10
Purchase #5	$119.68	9.648%	$131.2267	$131.23	$131.25	$131.20
Purchase #6	$192.69	12.138%	$216.0787	$216.08	$216.10	$216.10
Purchase #7	$128.79	7.542%	$138.5033	$138.50	$138.50	$138.50
7 purchase totals =	$929.65		$1,022.9353	$1,022.94	$1,022.95	$1,023.00