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	$206.69	4.289%	$215.5549	$215.55	$215.55	$215.60
Purchase #2	$215.92	10.531%	$238.6585	$238.66	$238.65	$238.70
Purchase #3	$68.78	11.189%	$76.4758	$76.48	$76.50	$76.50
Purchase #4	$212.90	4.596%	$222.6849	$222.68	$222.70	$222.70
Purchase #5	$233.40	10.613%	$258.1707	$258.17	$258.15	$258.20
Purchase #6	$51.75	13.143%	$58.5515	$58.55	$58.55	$58.60
Purchase #7	$137.59	5.848%	$145.6363	$145.64	$145.65	$145.60
7 purchase totals =	$1,127.03		$1,215.7326	$1,215.73	$1,215.75	$1,215.90