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	$49.37	10.486%	$54.5469	$54.55	$54.55	$54.50
Purchase #2	$24.93	10.651%	$27.5853	$27.59	$27.60	$27.60
Purchase #3	$164.41	11.630%	$183.5309	$183.53	$183.55	$183.50
Purchase #4	$213.71	6.542%	$227.6909	$227.69	$227.70	$227.70
Purchase #5	$174.59	11.412%	$194.5142	$194.51	$194.50	$194.50
Purchase #6	$144.52	7.822%	$155.8244	$155.82	$155.80	$155.80
Purchase #7	$220.99	10.490%	$244.1719	$244.17	$244.15	$244.20
7 purchase totals =	$992.52		$1,087.8645	$1,087.86	$1,087.85	$1,087.80