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	$26.98	3.225%	$27.8501	$27.85	$27.85	$27.90
Purchase #2	$120.64	8.337%	$130.6978	$130.70	$130.70	$130.70
Purchase #3	$19.42	10.851%	$21.5273	$21.53	$21.55	$21.50
Purchase #4	$125.88	10.731%	$139.3882	$139.39	$139.40	$139.40
Purchase #5	$186.41	5.159%	$196.0269	$196.03	$196.05	$196.00
Purchase #6	$188.73	13.628%	$214.4501	$214.45	$214.45	$214.50
Purchase #7	$139.35	9.312%	$152.3263	$152.33	$152.35	$152.30
7 purchase totals =	$807.41		$882.2667	$882.28	$882.35	$882.30