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	$76.38	9.726%	$83.8087	$83.81	$83.80	$83.80
Purchase #2	$120.68	5.296%	$127.0712	$127.07	$127.05	$127.10
Purchase #3	$22.71	5.793%	$24.0256	$24.03	$24.05	$24.00
Purchase #4	$109.71	6.140%	$116.4462	$116.45	$116.45	$116.40
Purchase #5	$34.78	10.386%	$38.3923	$38.39	$38.40	$38.40
Purchase #6	$89.45	12.235%	$100.3942	$100.39	$100.40	$100.40
Purchase #7	$101.88	9.283%	$111.3375	$111.34	$111.35	$111.30
7 purchase totals =	$555.59		$601.4757	$601.48	$601.50	$601.40