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	$226.85	6.122%	$240.7378	$240.74	$240.75	$240.70
Purchase #2	$96.93	5.823%	$102.5742	$102.57	$102.55	$102.60
Purchase #3	$71.53	9.778%	$78.5242	$78.52	$78.50	$78.50
Purchase #4	$57.27	9.671%	$62.8086	$62.81	$62.80	$62.80
Purchase #5	$132.38	6.764%	$141.3342	$141.33	$141.35	$141.30
Purchase #6	$230.86	13.591%	$262.2362	$262.24	$262.25	$262.20
Purchase #7	$118.68	3.777%	$123.1625	$123.16	$123.15	$123.20
7 purchase totals =	$934.50		$1,011.3777	$1,011.37	$1,011.35	$1,011.30