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	$140.47	4.362%	$146.5973	$146.60	$146.60	$146.60
Purchase #2	$83.84	4.240%	$87.3948	$87.39	$87.40	$87.40
Purchase #3	$163.83	11.292%	$182.3297	$182.33	$182.35	$182.30
Purchase #4	$164.77	6.467%	$175.4257	$175.43	$175.45	$175.40
Purchase #5	$166.38	11.288%	$185.161	$185.16	$185.15	$185.20
Purchase #6	$53.80	5.727%	$56.8811	$56.88	$56.90	$56.90
Purchase #7	$40.95	8.636%	$44.4864	$44.49	$44.50	$44.50
7 purchase totals =	$814.04		$878.2760	$878.28	$878.35	$878.30