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	$118.71	5.135%	$124.8058	$124.81	$124.80	$124.80
Purchase #2	$100.61	13.746%	$114.4399	$114.44	$114.45	$114.40
Purchase #3	$60.59	4.416%	$63.2657	$63.27	$63.25	$63.30
Purchase #4	$179.48	9.533%	$196.5898	$196.59	$196.60	$196.60
Purchase #5	$248.38	12.514%	$279.4623	$279.46	$279.45	$279.50
Purchase #6	$188.55	12.233%	$211.6153	$211.62	$211.60	$211.60
Purchase #7	$91.30	4.147%	$95.0862	$95.09	$95.10	$95.10
7 purchase totals =	$987.62		$1,085.2650	$1,085.28	$1,085.25	$1,085.30