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	$63.65	8.429%	$69.0151	$69.02	$69.00	$69.00
Purchase #2	$56.74	9.188%	$61.9533	$61.95	$61.95	$62.00
Purchase #3	$25.56	7.765%	$27.5447	$27.54	$27.55	$27.50
Purchase #4	$182.29	5.257%	$191.873	$191.87	$191.85	$191.90
Purchase #5	$237.54	7.359%	$255.0206	$255.02	$255.00	$255.00
Purchase #6	$76.40	9.393%	$83.5763	$83.58	$83.60	$83.60
Purchase #7	$28.54	12.577%	$32.1295	$32.13	$32.15	$32.10
7 purchase totals =	$670.72		$721.1125	$721.11	$721.10	$721.10