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	$166.88	4.104%	$173.7288	$173.73	$173.75	$173.70
Purchase #2	$195.49	7.582%	$210.3121	$210.31	$210.30	$210.30
Purchase #3	$98.66	13.522%	$112.0008	$112.00	$112.00	$112.00
Purchase #4	$189.35	4.262%	$197.4201	$197.42	$197.40	$197.40
Purchase #5	$94.44	6.648%	$100.7184	$100.72	$100.70	$100.70
Purchase #6	$138.37	4.134%	$144.0902	$144.09	$144.10	$144.10
Purchase #7	$244.53	5.557%	$258.1185	$258.12	$258.10	$258.10
7 purchase totals =	$1,127.72		$1,196.3889	$1,196.39	$1,196.35	$1,196.30