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	$18.49	4.691%	$19.3574	$19.36	$19.35	$19.40
Purchase #2	$38.47	6.680%	$41.0398	$41.04	$41.05	$41.00
Purchase #3	$81.90	9.631%	$89.7878	$89.79	$89.80	$89.80
Purchase #4	$52.84	4.803%	$55.3779	$55.38	$55.40	$55.40
Purchase #5	$19.29	3.236%	$19.9142	$19.91	$19.90	$19.90
Purchase #6	$98.85	7.187%	$105.9543	$105.95	$105.95	$106.00
Purchase #7	$38.33	3.258%	$39.5788	$39.58	$39.60	$39.60
7 purchase totals =	$348.17		$371.0102	$371.01	$371.05	$371.10