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	$136.69	5.676%	$144.4485	$144.45	$144.45	$144.40
Purchase #2	$91.80	3.132%	$94.6752	$94.68	$94.70	$94.70
Purchase #3	$81.29	13.317%	$92.1154	$92.12	$92.10	$92.10
Purchase #4	$138.55	9.493%	$151.7026	$151.70	$151.70	$151.70
Purchase #5	$34.40	8.323%	$37.2631	$37.26	$37.25	$37.30
Purchase #6	$78.48	13.410%	$89.0042	$89.00	$89.00	$89.00
Purchase #7	$130.92	10.448%	$144.5985	$144.60	$144.60	$144.60
7 purchase totals =	$692.13		$753.8075	$753.81	$753.80	$753.80