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	$185.94	9.767%	$204.1008	$204.10	$204.10	$204.10
Purchase #2	$155.35	7.429%	$166.891	$166.89	$166.90	$166.90
Purchase #3	$151.61	8.756%	$164.885	$164.89	$164.90	$164.90
Purchase #4	$90.55	12.298%	$101.6858	$101.69	$101.70	$101.70
Purchase #5	$29.81	12.377%	$33.4996	$33.50	$33.50	$33.50
Purchase #6	$77.29	4.177%	$80.5184	$80.52	$80.50	$80.50
Purchase #7	$65.63	3.262%	$67.7709	$67.77	$67.75	$67.80
7 purchase totals =	$756.18		$819.3515	$819.36	$819.35	$819.40