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	$208.28	5.393%	$219.5125	$219.51	$219.50	$219.50
Purchase #2	$186.46	5.119%	$196.0049	$196.00	$196.00	$196.00
Purchase #3	$159.71	11.506%	$178.0862	$178.09	$178.10	$178.10
Purchase #4	$142.28	5.677%	$150.3572	$150.36	$150.35	$150.40
Purchase #5	$130.80	9.660%	$143.4353	$143.44	$143.45	$143.40
Purchase #6	$135.44	6.717%	$144.5375	$144.54	$144.55	$144.50
Purchase #7	$235.43	8.785%	$256.1125	$256.11	$256.10	$256.10
7 purchase totals =	$1,198.40		$1,288.0461	$1,288.05	$1,288.05	$1,288.00