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	$174.60	6.364%	$185.7115	$185.71	$185.70	$185.70
Purchase #2	$80.57	6.522%	$85.8248	$85.82	$85.80	$85.80
Purchase #3	$73.43	13.239%	$83.1514	$83.15	$83.15	$83.20
Purchase #4	$96.52	8.652%	$104.8709	$104.87	$104.85	$104.90
Purchase #5	$213.87	5.217%	$225.0276	$225.03	$225.05	$225.00
Purchase #6	$128.31	12.342%	$144.146	$144.15	$144.15	$144.10
Purchase #7	$66.33	4.851%	$69.5477	$69.55	$69.55	$69.50
7 purchase totals =	$833.63		$898.2799	$898.28	$898.25	$898.20