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	$145.34	5.467%	$153.2857	$153.29	$153.30	$153.30
Purchase #2	$135.75	13.135%	$153.5808	$153.58	$153.60	$153.60
Purchase #3	$67.81	8.703%	$73.7115	$73.71	$73.70	$73.70
Purchase #4	$168.68	13.518%	$191.4822	$191.48	$191.50	$191.50
Purchase #5	$81.71	10.307%	$90.1318	$90.13	$90.15	$90.10
Purchase #6	$48.46	10.319%	$53.4606	$53.46	$53.45	$53.50
Purchase #7	$104.38	4.425%	$108.9988	$109.00	$109.00	$109.00
7 purchase totals =	$752.13		$824.6514	$824.65	$824.70	$824.70