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	$123.34	7.522%	$132.6176	$132.62	$132.60	$132.60
Purchase #2	$105.41	13.149%	$119.2704	$119.27	$119.25	$119.30
Purchase #3	$48.47	9.203%	$52.9307	$52.93	$52.95	$52.90
Purchase #4	$125.36	8.596%	$136.1359	$136.14	$136.15	$136.10
Purchase #5	$151.57	8.346%	$164.22	$164.22	$164.20	$164.20
Purchase #6	$88.94	12.734%	$100.2656	$100.27	$100.25	$100.30
Purchase #7	$36.92	3.191%	$38.0981	$38.10	$38.10	$38.10
7 purchase totals =	$680.01		$743.5383	$743.55	$743.50	$743.50