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	$59.77	4.183%	$62.2702	$62.27	$62.25	$62.30
Purchase #2	$114.89	11.344%	$127.9231	$127.92	$127.90	$127.90
Purchase #3	$144.31	6.408%	$153.5574	$153.56	$153.55	$153.60
Purchase #4	$83.94	13.442%	$95.2232	$95.22	$95.20	$95.20
Purchase #5	$237.90	7.348%	$255.3809	$255.38	$255.40	$255.40
Purchase #6	$189.42	6.466%	$201.6679	$201.67	$201.65	$201.70
Purchase #7	$69.41	13.588%	$78.8414	$78.84	$78.85	$78.80
7 purchase totals =	$899.64		$974.8641	$974.86	$974.80	$974.90