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	$105.93	5.487%	$111.7424	$111.74	$111.75	$111.70
Purchase #2	$43.51	3.612%	$45.0816	$45.08	$45.10	$45.10
Purchase #3	$185.38	3.187%	$191.2881	$191.29	$191.30	$191.30
Purchase #4	$196.46	7.713%	$211.613	$211.61	$211.60	$211.60
Purchase #5	$16.86	3.306%	$17.4174	$17.42	$17.40	$17.40
Purchase #6	$67.53	7.610%	$72.669	$72.67	$72.65	$72.70
Purchase #7	$16.46	4.262%	$17.1615	$17.16	$17.15	$17.20
7 purchase totals =	$632.13		$666.9730	$666.97	$666.95	$667.00