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	$57.96	7.726%	$62.438	$62.44	$62.45	$62.40
Purchase #2	$194.71	5.755%	$205.9156	$205.92	$205.90	$205.90
Purchase #3	$144.37	11.332%	$160.73	$160.73	$160.75	$160.70
Purchase #4	$164.79	4.785%	$172.6752	$172.68	$172.70	$172.70
Purchase #5	$160.28	3.355%	$165.6574	$165.66	$165.65	$165.70
Purchase #6	$133.72	9.628%	$146.5946	$146.59	$146.60	$146.60
Purchase #7	$157.28	6.383%	$167.3192	$167.32	$167.30	$167.30
7 purchase totals =	$1,013.11		$1,081.3300	$1,081.34	$1,081.35	$1,081.30