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	$80.84	5.686%	$85.4366	$85.44	$85.45	$85.40
Purchase #2	$107.50	9.870%	$118.1103	$118.11	$118.10	$118.10
Purchase #3	$81.25	11.110%	$90.2769	$90.28	$90.30	$90.30
Purchase #4	$200.41	11.612%	$223.6816	$223.68	$223.70	$223.70
Purchase #5	$74.34	4.242%	$77.4935	$77.49	$77.50	$77.50
Purchase #6	$199.31	3.149%	$205.5863	$205.59	$205.60	$205.60
Purchase #7	$110.91	10.456%	$122.5067	$122.51	$122.50	$122.50
7 purchase totals =	$854.56		$923.0919	$923.10	$923.15	$923.10