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	$233.67	4.486%	$244.1524	$244.15	$244.15	$244.20
Purchase #2	$52.43	10.334%	$57.8481	$57.85	$57.85	$57.80
Purchase #3	$240.46	6.684%	$256.5323	$256.53	$256.55	$256.50
Purchase #4	$70.55	5.757%	$74.6116	$74.61	$74.60	$74.60
Purchase #5	$151.80	3.141%	$156.568	$156.57	$156.55	$156.60
Purchase #6	$179.35	3.163%	$185.0228	$185.02	$185.00	$185.00
Purchase #7	$77.79	4.535%	$81.3178	$81.32	$81.30	$81.30
7 purchase totals =	$1,006.05		$1,056.0530	$1,056.05	$1,056.00	$1,056.00