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	$46.85	10.744%	$51.8836	$51.88	$51.90	$51.90
Purchase #2	$105.67	6.838%	$112.8957	$112.90	$112.90	$112.90
Purchase #3	$132.85	10.724%	$147.0968	$147.10	$147.10	$147.10
Purchase #4	$244.96	4.373%	$255.6721	$255.67	$255.65	$255.70
Purchase #5	$167.31	3.560%	$173.2662	$173.27	$173.25	$173.30
Purchase #6	$239.33	5.204%	$251.7847	$251.78	$251.80	$251.80
Purchase #7	$142.76	4.611%	$149.3427	$149.34	$149.35	$149.30
7 purchase totals =	$1,079.73		$1,141.9418	$1,141.94	$1,141.95	$1,142.00