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	$173.47	9.428%	$189.8248	$189.82	$189.80	$189.80
Purchase #2	$185.94	12.308%	$208.8255	$208.83	$208.85	$208.80
Purchase #3	$40.36	13.786%	$45.924	$45.92	$45.90	$45.90
Purchase #4	$216.94	3.275%	$224.0448	$224.04	$224.05	$224.00
Purchase #5	$144.77	6.852%	$154.6896	$154.69	$154.70	$154.70
Purchase #6	$148.32	8.369%	$160.7329	$160.73	$160.75	$160.70
Purchase #7	$135.86	5.706%	$143.6122	$143.61	$143.60	$143.60
7 purchase totals =	$1,045.66		$1,127.6538	$1,127.64	$1,127.65	$1,127.50