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	$100.29	6.549%	$106.858	$106.86	$106.85	$106.90
Purchase #2	$215.36	5.580%	$227.3771	$227.38	$227.40	$227.40
Purchase #3	$162.92	8.407%	$176.6167	$176.62	$176.60	$176.60
Purchase #4	$31.75	5.667%	$33.5493	$33.55	$33.55	$33.50
Purchase #5	$179.77	6.693%	$191.802	$191.80	$191.80	$191.80
Purchase #6	$238.90	6.795%	$255.1333	$255.13	$255.15	$255.10
Purchase #7	$39.70	9.366%	$43.4183	$43.42	$43.40	$43.40
7 purchase totals =	$968.69		$1,034.7547	$1,034.76	$1,034.75	$1,034.70