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	$160.94	9.598%	$176.387	$176.39	$176.40	$176.40
Purchase #2	$166.93	4.402%	$174.2783	$174.28	$174.30	$174.30
Purchase #3	$44.55	8.526%	$48.3483	$48.35	$48.35	$48.30
Purchase #4	$248.83	5.626%	$262.8292	$262.83	$262.85	$262.80
Purchase #5	$123.28	3.426%	$127.5036	$127.50	$127.50	$127.50
Purchase #6	$57.40	7.306%	$61.5936	$61.59	$61.60	$61.60
Purchase #7	$22.58	7.541%	$24.2828	$24.28	$24.30	$24.30
7 purchase totals =	$824.51		$875.2228	$875.22	$875.30	$875.20