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	$163.86	10.567%	$181.1751	$181.18	$181.20	$181.20
Purchase #2	$103.30	5.457%	$108.9371	$108.94	$108.95	$108.90
Purchase #3	$31.56	5.423%	$33.2715	$33.27	$33.25	$33.30
Purchase #4	$41.35	12.291%	$46.4323	$46.43	$46.45	$46.40
Purchase #5	$242.29	6.833%	$258.8457	$258.85	$258.85	$258.80
Purchase #6	$193.59	13.360%	$219.4536	$219.45	$219.45	$219.50
Purchase #7	$146.91	6.661%	$156.6957	$156.70	$156.70	$156.70
7 purchase totals =	$922.86		$1,004.8110	$1,004.82	$1,004.85	$1,004.80