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	$47.48	10.476%	$52.454	$52.45	$52.45	$52.50
Purchase #2	$41.81	13.735%	$47.5526	$47.55	$47.55	$47.60
Purchase #3	$85.98	5.577%	$90.7751	$90.78	$90.80	$90.80
Purchase #4	$112.58	4.640%	$117.8037	$117.80	$117.80	$117.80
Purchase #5	$205.61	8.141%	$222.3487	$222.35	$222.35	$222.30
Purchase #6	$124.90	12.773%	$140.8535	$140.85	$140.85	$140.90
Purchase #7	$16.75	6.733%	$17.8778	$17.88	$17.90	$17.90
7 purchase totals =	$635.11		$689.6654	$689.66	$689.70	$689.80