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	$75.59	4.728%	$79.1639	$79.16	$79.15	$79.20
Purchase #2	$206.95	5.517%	$218.3674	$218.37	$218.35	$218.40
Purchase #3	$229.60	11.260%	$255.453	$255.45	$255.45	$255.50
Purchase #4	$231.78	11.568%	$258.5923	$258.59	$258.60	$258.60
Purchase #5	$130.66	4.826%	$136.9657	$136.97	$136.95	$137.00
Purchase #6	$72.28	13.673%	$82.1628	$82.16	$82.15	$82.20
Purchase #7	$121.88	8.162%	$131.8278	$131.83	$131.85	$131.80
7 purchase totals =	$1,068.74		$1,162.5329	$1,162.53	$1,162.50	$1,162.70