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	$144.41	3.526%	$149.5019	$149.50	$149.50	$149.50
Purchase #2	$196.42	11.730%	$219.4601	$219.46	$219.45	$219.50
Purchase #3	$75.34	6.823%	$80.4804	$80.48	$80.50	$80.50
Purchase #4	$41.80	9.301%	$45.6878	$45.69	$45.70	$45.70
Purchase #5	$228.99	11.784%	$255.9742	$255.97	$255.95	$256.00
Purchase #6	$59.47	6.512%	$63.3427	$63.34	$63.35	$63.30
Purchase #7	$154.40	11.497%	$172.1514	$172.15	$172.15	$172.20
7 purchase totals =	$900.83		$986.5985	$986.59	$986.60	$986.70