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	$97.52	3.616%	$101.0463	$101.05	$101.05	$101.00
Purchase #2	$95.91	7.541%	$103.1426	$103.14	$103.15	$103.10
Purchase #3	$168.72	13.108%	$190.8358	$190.84	$190.85	$190.80
Purchase #4	$139.72	9.863%	$153.5006	$153.50	$153.50	$153.50
Purchase #5	$250.70	8.841%	$272.8644	$272.86	$272.85	$272.90
Purchase #6	$28.31	13.531%	$32.1406	$32.14	$32.15	$32.10
Purchase #7	$20.64	5.764%	$21.8297	$21.83	$21.85	$21.80
7 purchase totals =	$801.52		$875.3600	$875.36	$875.40	$875.20