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	$54.69	8.298%	$59.2282	$59.23	$59.25	$59.20
Purchase #2	$88.90	11.475%	$99.1013	$99.10	$99.10	$99.10
Purchase #3	$123.38	7.561%	$132.7088	$132.71	$132.70	$132.70
Purchase #4	$55.78	9.865%	$61.2827	$61.28	$61.30	$61.30
Purchase #5	$190.45	8.761%	$207.1353	$207.14	$207.15	$207.10
Purchase #6	$51.75	5.864%	$54.7846	$54.78	$54.80	$54.80
Purchase #7	$218.61	8.426%	$237.0301	$237.03	$237.05	$237.00
7 purchase totals =	$783.56		$851.2710	$851.27	$851.35	$851.20