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	$220.64	8.103%	$238.5185	$238.52	$238.50	$238.50
Purchase #2	$121.90	4.438%	$127.3099	$127.31	$127.30	$127.30
Purchase #3	$198.72	13.625%	$225.7956	$225.80	$225.80	$225.80
Purchase #4	$237.56	10.523%	$262.5584	$262.56	$262.55	$262.60
Purchase #5	$97.88	5.131%	$102.9022	$102.90	$102.90	$102.90
Purchase #6	$100.28	6.800%	$107.099	$107.10	$107.10	$107.10
Purchase #7	$41.89	8.187%	$45.3195	$45.32	$45.30	$45.30
7 purchase totals =	$1,018.87		$1,109.5031	$1,109.51	$1,109.45	$1,109.50