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	$215.93	3.130%	$222.6886	$222.69	$222.70	$222.70
Purchase #2	$191.47	4.796%	$200.6529	$200.65	$200.65	$200.70
Purchase #3	$219.53	5.453%	$231.501	$231.50	$231.50	$231.50
Purchase #4	$48.97	5.269%	$51.5502	$51.55	$51.55	$51.60
Purchase #5	$139.66	10.602%	$154.4668	$154.47	$154.45	$154.50
Purchase #6	$73.76	10.553%	$81.5439	$81.54	$81.55	$81.50
Purchase #7	$49.27	7.276%	$52.8549	$52.85	$52.85	$52.90
7 purchase totals =	$938.59		$995.2583	$995.25	$995.25	$995.40