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	$153.39	10.760%	$169.8948	$169.89	$169.90	$169.90
Purchase #2	$166.80	11.288%	$185.6284	$185.63	$185.65	$185.60
Purchase #3	$156.96	4.551%	$164.1032	$164.10	$164.10	$164.10
Purchase #4	$241.93	8.634%	$262.8182	$262.82	$262.80	$262.80
Purchase #5	$98.36	12.395%	$110.5517	$110.55	$110.55	$110.60
Purchase #6	$33.51	5.257%	$35.2716	$35.27	$35.25	$35.30
Purchase #7	$128.37	11.522%	$143.1608	$143.16	$143.15	$143.20
7 purchase totals =	$979.32		$1,071.4287	$1,071.42	$1,071.40	$1,071.50