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	$83.28	5.144%	$87.5639	$87.56	$87.55	$87.60
Purchase #2	$150.78	5.740%	$159.4348	$159.43	$159.45	$159.40
Purchase #3	$115.80	9.804%	$127.153	$127.15	$127.15	$127.20
Purchase #4	$249.42	12.480%	$280.5476	$280.55	$280.55	$280.50
Purchase #5	$138.99	5.513%	$146.6525	$146.65	$146.65	$146.70
Purchase #6	$92.81	4.466%	$96.9549	$96.95	$96.95	$97.00
Purchase #7	$173.64	7.797%	$187.1787	$187.18	$187.20	$187.20
7 purchase totals =	$1,004.72		$1,085.4854	$1,085.47	$1,085.50	$1,085.60