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	$192.54	8.277%	$208.4765	$208.48	$208.50	$208.50
Purchase #2	$40.92	10.590%	$45.2534	$45.25	$45.25	$45.30
Purchase #3	$62.52	4.238%	$65.1696	$65.17	$65.15	$65.20
Purchase #4	$35.74	13.857%	$40.6925	$40.69	$40.70	$40.70
Purchase #5	$138.51	10.256%	$152.7156	$152.72	$152.70	$152.70
Purchase #6	$82.59	6.178%	$87.6924	$87.69	$87.70	$87.70
Purchase #7	$166.79	10.354%	$184.0594	$184.06	$184.05	$184.10
7 purchase totals =	$719.61		$784.0594	$784.06	$784.05	$784.20