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	$164.64	9.302%	$179.9548	$179.95	$179.95	$180.00
Purchase #2	$49.73	9.103%	$54.2569	$54.26	$54.25	$54.30
Purchase #3	$82.40	13.504%	$93.5273	$93.53	$93.55	$93.50
Purchase #4	$135.59	6.842%	$144.8671	$144.87	$144.85	$144.90
Purchase #5	$124.73	9.790%	$136.9411	$136.94	$136.95	$136.90
Purchase #6	$166.59	7.367%	$178.8627	$178.86	$178.85	$178.90
Purchase #7	$249.56	13.180%	$282.452	$282.45	$282.45	$282.50
7 purchase totals =	$973.24		$1,070.8619	$1,070.86	$1,070.85	$1,071.00