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	$240.87	7.178%	$258.1596	$258.16	$258.15	$258.20
Purchase #2	$35.32	5.616%	$37.3036	$37.30	$37.30	$37.30
Purchase #3	$174.97	12.354%	$196.5858	$196.59	$196.60	$196.60
Purchase #4	$136.94	12.766%	$154.4218	$154.42	$154.40	$154.40
Purchase #5	$248.43	4.484%	$259.5696	$259.57	$259.55	$259.60
Purchase #6	$76.65	4.583%	$80.1629	$80.16	$80.15	$80.20
Purchase #7	$67.32	8.197%	$72.8382	$72.84	$72.85	$72.80
7 purchase totals =	$980.50		$1,059.0415	$1,059.04	$1,059.00	$1,059.10