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	$221.48	4.552%	$231.5618	$231.56	$231.55	$231.60
Purchase #2	$78.64	8.786%	$85.5493	$85.55	$85.55	$85.50
Purchase #3	$63.63	7.315%	$68.2845	$68.28	$68.30	$68.30
Purchase #4	$89.81	10.390%	$99.1413	$99.14	$99.15	$99.10
Purchase #5	$186.48	10.392%	$205.859	$205.86	$205.85	$205.90
Purchase #6	$97.37	10.622%	$107.7126	$107.71	$107.70	$107.70
Purchase #7	$207.92	5.129%	$218.5842	$218.58	$218.60	$218.60
7 purchase totals =	$945.33		$1,016.6927	$1,016.68	$1,016.70	$1,016.70