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	$56.83	4.338%	$59.2953	$59.30	$59.30	$59.30
Purchase #2	$101.70	4.602%	$106.3802	$106.38	$106.40	$106.40
Purchase #3	$125.40	11.112%	$139.3344	$139.33	$139.35	$139.30
Purchase #4	$82.72	8.102%	$89.422	$89.42	$89.40	$89.40
Purchase #5	$100.58	3.274%	$103.873	$103.87	$103.85	$103.90
Purchase #6	$97.93	5.650%	$103.463	$103.46	$103.45	$103.50
Purchase #7	$115.35	8.188%	$124.7949	$124.79	$124.80	$124.80
7 purchase totals =	$680.51		$726.5628	$726.55	$726.55	$726.60