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	$189.54	9.847%	$208.204	$208.20	$208.20	$208.20
Purchase #2	$28.61	9.180%	$31.2364	$31.24	$31.25	$31.20
Purchase #3	$63.76	12.173%	$71.5215	$71.52	$71.50	$71.50
Purchase #4	$52.29	4.454%	$54.619	$54.62	$54.60	$54.60
Purchase #5	$95.52	8.338%	$103.4845	$103.48	$103.50	$103.50
Purchase #6	$17.97	3.602%	$18.6173	$18.62	$18.60	$18.60
Purchase #7	$169.59	9.329%	$185.4111	$185.41	$185.40	$185.40
7 purchase totals =	$617.28		$673.0938	$673.09	$673.05	$673.00