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	$210.68	6.539%	$224.4564	$224.46	$224.45	$224.50
Purchase #2	$68.58	13.531%	$77.8596	$77.86	$77.85	$77.90
Purchase #3	$56.44	4.581%	$59.0255	$59.03	$59.05	$59.00
Purchase #4	$169.90	7.622%	$182.8498	$182.85	$182.85	$182.80
Purchase #5	$187.85	9.326%	$205.3689	$205.37	$205.35	$205.40
Purchase #6	$209.77	9.365%	$229.415	$229.42	$229.40	$229.40
Purchase #7	$22.46	9.636%	$24.6242	$24.62	$24.60	$24.60
7 purchase totals =	$925.68		$1,003.5994	$1,003.61	$1,003.55	$1,003.60