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	$238.86	4.209%	$248.9136	$248.91	$248.90	$248.90
Purchase #2	$206.40	12.323%	$231.8347	$231.83	$231.85	$231.80
Purchase #3	$105.51	7.219%	$113.1268	$113.13	$113.15	$113.10
Purchase #4	$88.88	12.681%	$100.1509	$100.15	$100.15	$100.20
Purchase #5	$52.26	8.508%	$56.7063	$56.71	$56.70	$56.70
Purchase #6	$105.81	10.604%	$117.0301	$117.03	$117.05	$117.00
Purchase #7	$193.78	12.839%	$218.6594	$218.66	$218.65	$218.70
7 purchase totals =	$991.50		$1,086.4218	$1,086.42	$1,086.45	$1,086.40