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	$188.82	5.680%	$199.545	$199.55	$199.55	$199.50
Purchase #2	$245.70	10.866%	$272.3978	$272.40	$272.40	$272.40
Purchase #3	$102.82	10.465%	$113.5801	$113.58	$113.60	$113.60
Purchase #4	$238.93	4.387%	$249.4119	$249.41	$249.40	$249.40
Purchase #5	$91.37	5.768%	$96.6402	$96.64	$96.65	$96.60
Purchase #6	$124.51	9.835%	$136.7556	$136.76	$136.75	$136.80
Purchase #7	$118.90	7.693%	$128.047	$128.05	$128.05	$128.00
7 purchase totals =	$1,111.05		$1,196.3776	$1,196.39	$1,196.40	$1,196.30