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	$162.32	13.861%	$184.8192	$184.82	$184.80	$184.80
Purchase #2	$150.88	11.561%	$168.3232	$168.32	$168.30	$168.30
Purchase #3	$101.81	5.606%	$107.5175	$107.52	$107.50	$107.50
Purchase #4	$52.48	8.360%	$56.8673	$56.87	$56.85	$56.90
Purchase #5	$103.71	11.182%	$115.3069	$115.31	$115.30	$115.30
Purchase #6	$82.64	8.589%	$89.7379	$89.74	$89.75	$89.70
Purchase #7	$99.60	7.402%	$106.9724	$106.97	$106.95	$107.00
7 purchase totals =	$753.44		$829.5444	$829.55	$829.45	$829.50