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	$178.44	3.406%	$184.5177	$184.52	$184.50	$184.50
Purchase #2	$104.85	4.294%	$109.3523	$109.35	$109.35	$109.40
Purchase #3	$36.31	6.118%	$38.5314	$38.53	$38.55	$38.50
Purchase #4	$137.61	13.718%	$156.4873	$156.49	$156.50	$156.50
Purchase #5	$86.39	4.588%	$90.3536	$90.35	$90.35	$90.40
Purchase #6	$204.26	9.845%	$224.3694	$224.37	$224.35	$224.40
Purchase #7	$214.86	6.149%	$228.0717	$228.07	$228.05	$228.10
7 purchase totals =	$962.72		$1,031.6834	$1,031.68	$1,031.65	$1,031.80