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	$227.85	4.698%	$238.5544	$238.55	$238.55	$238.60
Purchase #2	$198.90	8.664%	$216.1327	$216.13	$216.15	$216.10
Purchase #3	$112.77	11.583%	$125.8321	$125.83	$125.85	$125.80
Purchase #4	$128.32	12.451%	$144.2971	$144.30	$144.30	$144.30
Purchase #5	$121.61	9.565%	$133.242	$133.24	$133.25	$133.20
Purchase #6	$48.32	10.646%	$53.4641	$53.46	$53.45	$53.50
Purchase #7	$165.54	6.551%	$176.3845	$176.38	$176.40	$176.40
7 purchase totals =	$1,003.31		$1,087.9069	$1,087.89	$1,087.95	$1,087.90