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	$135.41	13.382%	$153.5306	$153.53	$153.55	$153.50
Purchase #2	$170.42	9.405%	$186.448	$186.45	$186.45	$186.40
Purchase #3	$38.74	7.334%	$41.5812	$41.58	$41.60	$41.60
Purchase #4	$138.58	11.400%	$154.3781	$154.38	$154.40	$154.40
Purchase #5	$104.82	6.587%	$111.7245	$111.72	$111.70	$111.70
Purchase #6	$173.57	6.200%	$184.3313	$184.33	$184.35	$184.30
Purchase #7	$164.80	13.257%	$186.6475	$186.65	$186.65	$186.60
7 purchase totals =	$926.34		$1,018.6412	$1,018.64	$1,018.70	$1,018.50