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	$78.64	10.846%	$87.1693	$87.17	$87.15	$87.20
Purchase #2	$41.47	5.287%	$43.6625	$43.66	$43.65	$43.70
Purchase #3	$196.82	5.449%	$207.5447	$207.54	$207.55	$207.50
Purchase #4	$28.83	12.177%	$32.3406	$32.34	$32.35	$32.30
Purchase #5	$82.86	8.345%	$89.7747	$89.77	$89.75	$89.80
Purchase #6	$236.45	9.280%	$258.3926	$258.39	$258.40	$258.40
Purchase #7	$202.50	6.257%	$215.1704	$215.17	$215.15	$215.20
7 purchase totals =	$867.57		$934.0548	$934.04	$934.00	$934.10