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	$248.79	4.797%	$260.7245	$260.72	$260.70	$260.70
Purchase #2	$35.68	5.173%	$37.5257	$37.53	$37.55	$37.50
Purchase #3	$95.86	8.346%	$103.8605	$103.86	$103.85	$103.90
Purchase #4	$228.91	4.388%	$238.9546	$238.95	$238.95	$239.00
Purchase #5	$153.67	12.480%	$172.848	$172.85	$172.85	$172.80
Purchase #6	$47.57	10.555%	$52.591	$52.59	$52.60	$52.60
Purchase #7	$197.80	11.333%	$220.2167	$220.22	$220.20	$220.20
7 purchase totals =	$1,008.28		$1,086.7210	$1,086.72	$1,086.70	$1,086.70