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	$65.56	3.292%	$67.7182	$67.72	$67.70	$67.70
Purchase #2	$247.80	13.338%	$280.8516	$280.85	$280.85	$280.90
Purchase #3	$148.43	9.431%	$162.4284	$162.43	$162.45	$162.40
Purchase #4	$131.99	10.602%	$145.9836	$145.98	$146.00	$146.00
Purchase #5	$178.75	4.246%	$186.3397	$186.34	$186.35	$186.30
Purchase #6	$36.43	6.825%	$38.9163	$38.92	$38.90	$38.90
Purchase #7	$103.37	8.645%	$112.3063	$112.31	$112.30	$112.30
7 purchase totals =	$912.33		$994.5441	$994.55	$994.55	$994.50