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	$136.64	10.109%	$150.4529	$150.45	$150.45	$150.50
Purchase #2	$84.35	13.378%	$95.6343	$95.63	$95.65	$95.60
Purchase #3	$127.85	11.501%	$142.554	$142.55	$142.55	$142.60
Purchase #4	$70.34	9.539%	$77.0497	$77.05	$77.05	$77.00
Purchase #5	$40.58	13.516%	$46.0648	$46.06	$46.05	$46.10
Purchase #6	$99.93	3.611%	$103.5385	$103.54	$103.55	$103.50
Purchase #7	$56.28	9.239%	$61.4797	$61.48	$61.50	$61.50
7 purchase totals =	$615.97		$676.7739	$676.76	$676.80	$676.80