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	$108.74	7.361%	$116.7444	$116.74	$116.75	$116.70
Purchase #2	$204.80	3.846%	$212.6766	$212.68	$212.70	$212.70
Purchase #3	$59.53	10.272%	$65.6449	$65.64	$65.65	$65.60
Purchase #4	$140.42	3.572%	$145.4358	$145.44	$145.45	$145.40
Purchase #5	$129.71	11.663%	$144.8381	$144.84	$144.85	$144.80
Purchase #6	$148.77	13.487%	$168.8346	$168.83	$168.85	$168.80
Purchase #7	$138.35	9.391%	$151.3424	$151.34	$151.35	$151.30
7 purchase totals =	$930.32		$1,005.5168	$1,005.51	$1,005.60	$1,005.30