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	$241.63	5.509%	$254.9414	$254.94	$254.95	$254.90
Purchase #2	$224.60	7.146%	$240.6499	$240.65	$240.65	$240.60
Purchase #3	$76.41	13.793%	$86.9492	$86.95	$86.95	$86.90
Purchase #4	$99.42	4.271%	$103.6662	$103.67	$103.65	$103.70
Purchase #5	$26.76	4.487%	$27.9607	$27.96	$27.95	$28.00
Purchase #6	$221.48	10.680%	$245.1341	$245.13	$245.15	$245.10
Purchase #7	$174.93	9.346%	$191.279	$191.28	$191.30	$191.30
7 purchase totals =	$1,065.23		$1,150.5805	$1,150.58	$1,150.60	$1,150.50