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	$242.45	5.514%	$255.8187	$255.82	$255.80	$255.80
Purchase #2	$67.75	6.427%	$72.1043	$72.10	$72.10	$72.10
Purchase #3	$44.59	3.292%	$46.0579	$46.06	$46.05	$46.10
Purchase #4	$214.37	12.499%	$241.1641	$241.16	$241.15	$241.20
Purchase #5	$89.44	6.794%	$95.5166	$95.52	$95.50	$95.50
Purchase #6	$107.42	7.599%	$115.5828	$115.58	$115.60	$115.60
Purchase #7	$77.47	11.633%	$86.4821	$86.48	$86.50	$86.50
7 purchase totals =	$843.49		$912.7265	$912.72	$912.70	$912.80