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	$104.34	9.759%	$114.5225	$114.52	$114.50	$114.50
Purchase #2	$28.32	3.574%	$29.3322	$29.33	$29.35	$29.30
Purchase #3	$83.50	7.632%	$89.8727	$89.87	$89.85	$89.90
Purchase #4	$182.87	10.492%	$202.0567	$202.06	$202.05	$202.10
Purchase #5	$78.71	4.456%	$82.2173	$82.22	$82.20	$82.20
Purchase #6	$214.66	4.262%	$223.8088	$223.81	$223.80	$223.80
Purchase #7	$25.62	11.241%	$28.4999	$28.50	$28.50	$28.50
7 purchase totals =	$718.02		$770.3101	$770.31	$770.25	$770.30