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	$180.55	8.601%	$196.0791	$196.08	$196.10	$196.10
Purchase #2	$135.94	5.428%	$143.3188	$143.32	$143.30	$143.30
Purchase #3	$18.39	11.214%	$20.4523	$20.45	$20.45	$20.50
Purchase #4	$40.58	8.277%	$43.9388	$43.94	$43.95	$43.90
Purchase #5	$204.99	6.480%	$218.2734	$218.27	$218.25	$218.30
Purchase #6	$107.45	8.395%	$116.4704	$116.47	$116.45	$116.50
Purchase #7	$39.56	7.350%	$42.4677	$42.47	$42.45	$42.50
7 purchase totals =	$727.46		$781.0005	$781.00	$780.95	$781.10