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	$198.93	10.240%	$219.3004	$219.30	$219.30	$219.30
Purchase #2	$7.69	5.615%	$8.1218	$8.12	$8.10	$8.10
Purchase #3	$116.28	12.205%	$130.472	$130.47	$130.45	$130.50
Purchase #4	$205.86	12.396%	$231.3784	$231.38	$231.40	$231.40
Purchase #5	$15.89	4.570%	$16.6162	$16.62	$16.60	$16.60
Purchase #6	$65.87	10.340%	$72.681	$72.68	$72.70	$72.70
Purchase #7	$19.90	9.829%	$21.856	$21.86	$21.85	$21.90
7 purchase totals =	$630.42		$700.4258	$700.43	$700.40	$700.50