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	$68.85	9.407%	$75.3267	$75.33	$75.35	$75.30
Purchase #2	$73.65	4.588%	$77.0291	$77.03	$77.05	$77.00
Purchase #3	$54.37	9.434%	$59.4993	$59.50	$59.50	$59.50
Purchase #4	$111.83	6.791%	$119.4244	$119.42	$119.40	$119.40
Purchase #5	$80.29	3.151%	$82.8199	$82.82	$82.80	$82.80
Purchase #6	$59.38	5.349%	$62.5562	$62.56	$62.55	$62.60
Purchase #7	$228.76	5.540%	$241.4333	$241.43	$241.45	$241.40
7 purchase totals =	$677.13		$718.0889	$718.09	$718.10	$718.00