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	$206.63	7.684%	$222.5074	$222.51	$222.50	$222.50
Purchase #2	$19.64	9.277%	$21.462	$21.46	$21.45	$21.50
Purchase #3	$62.65	7.470%	$67.33	$67.33	$67.35	$67.30
Purchase #4	$24.58	5.198%	$25.8577	$25.86	$25.85	$25.90
Purchase #5	$186.39	10.486%	$205.9349	$205.93	$205.95	$205.90
Purchase #6	$150.81	10.551%	$166.722	$166.72	$166.70	$166.70
Purchase #7	$85.86	9.186%	$93.7471	$93.75	$93.75	$93.70
7 purchase totals =	$736.56		$803.5611	$803.56	$803.55	$803.50