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	$173.25	3.808%	$179.8474	$179.85	$179.85	$179.80
Purchase #2	$234.29	11.561%	$261.3763	$261.38	$261.40	$261.40
Purchase #3	$166.47	4.695%	$174.2858	$174.29	$174.30	$174.30
Purchase #4	$96.94	9.159%	$105.8187	$105.82	$105.80	$105.80
Purchase #5	$32.70	3.356%	$33.7974	$33.80	$33.80	$33.80
Purchase #6	$139.26	13.836%	$158.528	$158.53	$158.55	$158.50
Purchase #7	$133.65	6.769%	$142.6968	$142.70	$142.70	$142.70
7 purchase totals =	$976.56		$1,056.3504	$1,056.37	$1,056.40	$1,056.30