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	$102.98	8.143%	$111.3657	$111.37	$111.35	$111.40
Purchase #2	$90.66	9.262%	$99.0569	$99.06	$99.05	$99.10
Purchase #3	$145.35	11.355%	$161.8545	$161.85	$161.85	$161.90
Purchase #4	$77.78	3.147%	$80.2277	$80.23	$80.25	$80.20
Purchase #5	$47.52	12.490%	$53.4552	$53.46	$53.45	$53.50
Purchase #6	$39.61	6.232%	$42.0785	$42.08	$42.10	$42.10
Purchase #7	$154.42	4.289%	$161.0431	$161.04	$161.05	$161.00
7 purchase totals =	$658.32		$709.0816	$709.09	$709.10	$709.20