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	$103.81	4.810%	$108.8033	$108.80	$108.80	$108.80
Purchase #2	$67.33	12.518%	$75.7584	$75.76	$75.75	$75.80
Purchase #3	$102.53	3.141%	$105.7505	$105.75	$105.75	$105.80
Purchase #4	$137.38	10.107%	$151.265	$151.27	$151.25	$151.30
Purchase #5	$172.49	5.156%	$181.3836	$181.38	$181.40	$181.40
Purchase #6	$45.44	6.710%	$48.489	$48.49	$48.50	$48.50
Purchase #7	$44.45	5.520%	$46.9036	$46.90	$46.90	$46.90
7 purchase totals =	$673.43		$718.3534	$718.35	$718.35	$718.50