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	$159.94	7.696%	$172.249	$172.25	$172.25	$172.20
Purchase #2	$108.31	11.531%	$120.7992	$120.80	$120.80	$120.80
Purchase #3	$180.39	4.421%	$188.365	$188.37	$188.35	$188.40
Purchase #4	$121.68	5.116%	$127.9051	$127.91	$127.90	$127.90
Purchase #5	$90.35	4.431%	$94.3534	$94.35	$94.35	$94.40
Purchase #6	$198.41	8.828%	$215.9256	$215.93	$215.95	$215.90
Purchase #7	$216.85	3.789%	$225.0664	$225.07	$225.05	$225.10
7 purchase totals =	$1,075.93		$1,144.6637	$1,144.68	$1,144.65	$1,144.70