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	$201.81	12.828%	$227.6982	$227.70	$227.70	$227.70
Purchase #2	$139.51	10.343%	$153.9395	$153.94	$153.95	$153.90
Purchase #3	$154.96	10.360%	$171.0139	$171.01	$171.00	$171.00
Purchase #4	$127.36	13.533%	$144.5956	$144.60	$144.60	$144.60
Purchase #5	$132.33	11.500%	$147.548	$147.55	$147.55	$147.50
Purchase #6	$189.47	7.549%	$203.7731	$203.77	$203.75	$203.80
Purchase #7	$69.96	12.320%	$78.5791	$78.58	$78.60	$78.60
7 purchase totals =	$1,015.40		$1,127.1474	$1,127.15	$1,127.15	$1,127.10