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	$143.69	4.796%	$150.5814	$150.58	$150.60	$150.60
Purchase #2	$98.73	7.833%	$106.4635	$106.46	$106.45	$106.50
Purchase #3	$166.39	11.752%	$185.9442	$185.94	$185.95	$185.90
Purchase #4	$154.87	11.601%	$172.8365	$172.84	$172.85	$172.80
Purchase #5	$118.60	13.358%	$134.4426	$134.44	$134.45	$134.40
Purchase #6	$139.33	13.423%	$158.0323	$158.03	$158.05	$158.00
Purchase #7	$123.93	10.315%	$136.7134	$136.71	$136.70	$136.70
7 purchase totals =	$945.54		$1,045.0139	$1,045.00	$1,045.05	$1,044.90