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	$78.28	5.833%	$82.8461	$82.85	$82.85	$82.80
Purchase #2	$91.42	5.684%	$96.6163	$96.62	$96.60	$96.60
Purchase #3	$100.42	3.417%	$103.8514	$103.85	$103.85	$103.90
Purchase #4	$17.63	4.829%	$18.4814	$18.48	$18.50	$18.50
Purchase #5	$44.77	5.542%	$47.2512	$47.25	$47.25	$47.30
Purchase #6	$150.49	5.564%	$158.8633	$158.86	$158.85	$158.90
Purchase #7	$53.52	7.689%	$57.6352	$57.64	$57.65	$57.60
7 purchase totals =	$536.53		$565.5449	$565.55	$565.55	$565.60