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	$81.33	9.549%	$89.0962	$89.10	$89.10	$89.10
Purchase #2	$52.68	12.679%	$59.3593	$59.36	$59.35	$59.40
Purchase #3	$12.68	12.458%	$14.2597	$14.26	$14.25	$14.30
Purchase #4	$47.80	8.159%	$51.7	$51.70	$51.70	$51.70
Purchase #5	$103.92	5.517%	$109.6533	$109.65	$109.65	$109.70
Purchase #6	$115.33	13.186%	$130.5374	$130.54	$130.55	$130.50
Purchase #7	$180.35	10.695%	$199.6384	$199.64	$199.65	$199.60
7 purchase totals =	$594.09		$654.2443	$654.25	$654.25	$654.30