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	$158.55	5.819%	$167.776	$167.78	$167.80	$167.80
Purchase #2	$50.39	6.173%	$53.5006	$53.50	$53.50	$53.50
Purchase #3	$118.50	11.520%	$132.1512	$132.15	$132.15	$132.20
Purchase #4	$45.71	12.574%	$51.4576	$51.46	$51.45	$51.50
Purchase #5	$76.58	4.838%	$80.2849	$80.28	$80.30	$80.30
Purchase #6	$208.69	11.196%	$232.0549	$232.05	$232.05	$232.10
Purchase #7	$90.61	11.782%	$101.2857	$101.29	$101.30	$101.30
7 purchase totals =	$749.03		$818.5109	$818.51	$818.55	$818.70