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	$84.94	12.712%	$95.7376	$95.74	$95.75	$95.70
Purchase #2	$123.57	11.225%	$137.4407	$137.44	$137.45	$137.40
Purchase #3	$29.78	10.584%	$32.9319	$32.93	$32.95	$32.90
Purchase #4	$231.73	13.457%	$262.9139	$262.91	$262.90	$262.90
Purchase #5	$48.43	11.505%	$54.0019	$54.00	$54.00	$54.00
Purchase #6	$55.82	6.684%	$59.551	$59.55	$59.55	$59.60
Purchase #7	$67.30	6.396%	$71.6045	$71.60	$71.60	$71.60
7 purchase totals =	$641.57		$714.1815	$714.17	$714.20	$714.10