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	$119.61	8.865%	$130.2134	$130.21	$130.20	$130.20
Purchase #2	$73.53	10.797%	$81.469	$81.47	$81.45	$81.50
Purchase #3	$49.92	11.783%	$55.8021	$55.80	$55.80	$55.80
Purchase #4	$199.75	4.866%	$209.4698	$209.47	$209.45	$209.50
Purchase #5	$116.51	13.254%	$131.9522	$131.95	$131.95	$132.00
Purchase #6	$127.94	10.461%	$141.3238	$141.32	$141.30	$141.30
Purchase #7	$77.48	7.620%	$83.384	$83.38	$83.40	$83.40
7 purchase totals =	$764.74		$833.6143	$833.60	$833.55	$833.70