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	$219.55	3.585%	$227.4209	$227.42	$227.40	$227.40
Purchase #2	$202.47	3.433%	$209.4208	$209.42	$209.40	$209.40
Purchase #3	$126.52	6.401%	$134.6185	$134.62	$134.60	$134.60
Purchase #4	$248.42	9.562%	$272.1739	$272.17	$272.15	$272.20
Purchase #5	$127.50	10.489%	$140.8735	$140.87	$140.85	$140.90
Purchase #6	$36.54	5.246%	$38.4569	$38.46	$38.45	$38.50
Purchase #7	$69.62	4.617%	$72.8344	$72.83	$72.85	$72.80
7 purchase totals =	$1,030.62		$1,095.7989	$1,095.79	$1,095.70	$1,095.80