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	$128.78	6.859%	$137.613	$137.61	$137.60	$137.60
Purchase #2	$122.76	4.670%	$128.4929	$128.49	$128.50	$128.50
Purchase #3	$194.82	13.790%	$221.6857	$221.69	$221.70	$221.70
Purchase #4	$33.87	10.327%	$37.3678	$37.37	$37.35	$37.40
Purchase #5	$174.70	5.409%	$184.1495	$184.15	$184.15	$184.10
Purchase #6	$141.87	7.718%	$152.8195	$152.82	$152.80	$152.80
Purchase #7	$31.50	6.183%	$33.4476	$33.45	$33.45	$33.40
7 purchase totals =	$828.30		$895.5760	$895.58	$895.55	$895.50