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	$114.70	11.177%	$127.52	$127.52	$127.50	$127.50
Purchase #2	$214.90	9.547%	$235.4165	$235.42	$235.40	$235.40
Purchase #3	$109.86	12.313%	$123.3871	$123.39	$123.40	$123.40
Purchase #4	$89.74	12.387%	$100.8561	$100.86	$100.85	$100.90
Purchase #5	$187.81	3.481%	$194.3477	$194.35	$194.35	$194.30
Purchase #6	$140.29	6.177%	$148.9557	$148.96	$148.95	$149.00
Purchase #7	$88.68	5.136%	$93.2346	$93.23	$93.25	$93.20
7 purchase totals =	$945.98		$1,023.7177	$1,023.73	$1,023.70	$1,023.70