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	$93.86	8.550%	$101.885	$101.89	$101.90	$101.90
Purchase #2	$71.42	10.823%	$79.1498	$79.15	$79.15	$79.10
Purchase #3	$65.47	10.818%	$72.5525	$72.55	$72.55	$72.60
Purchase #4	$50.88	5.232%	$53.542	$53.54	$53.55	$53.50
Purchase #5	$141.58	13.395%	$160.5446	$160.54	$160.55	$160.50
Purchase #6	$5.27	5.129%	$5.5403	$5.54	$5.55	$5.50
Purchase #7	$107.75	5.688%	$113.8788	$113.88	$113.90	$113.90
7 purchase totals =	$536.23		$587.0930	$587.09	$587.15	$587.00