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	$239.83	10.578%	$265.1992	$265.20	$265.20	$265.20
Purchase #2	$163.37	11.693%	$182.4729	$182.47	$182.45	$182.50
Purchase #3	$111.95	5.865%	$118.5159	$118.52	$118.50	$118.50
Purchase #4	$93.95	6.113%	$99.6932	$99.69	$99.70	$99.70
Purchase #5	$118.34	7.352%	$127.0404	$127.04	$127.05	$127.00
Purchase #6	$238.61	12.133%	$267.5606	$267.56	$267.55	$267.60
Purchase #7	$114.64	8.655%	$124.5621	$124.56	$124.55	$124.60
7 purchase totals =	$1,080.69		$1,185.0443	$1,185.04	$1,185.00	$1,185.10