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	$200.58	9.196%	$219.0253	$219.03	$219.05	$219.00
Purchase #2	$220.41	9.604%	$241.5782	$241.58	$241.60	$241.60
Purchase #3	$168.91	4.545%	$176.587	$176.59	$176.60	$176.60
Purchase #4	$229.37	11.424%	$255.5732	$255.57	$255.55	$255.60
Purchase #5	$49.85	13.774%	$56.7163	$56.72	$56.70	$56.70
Purchase #6	$38.81	4.654%	$40.6162	$40.62	$40.60	$40.60
Purchase #7	$147.75	12.242%	$165.8376	$165.84	$165.85	$165.80
7 purchase totals =	$1,055.68		$1,155.9338	$1,155.95	$1,155.95	$1,155.90