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	$248.94	13.484%	$282.5071	$282.51	$282.50	$282.50
Purchase #2	$42.83	4.734%	$44.8576	$44.86	$44.85	$44.90
Purchase #3	$75.33	4.354%	$78.6099	$78.61	$78.60	$78.60
Purchase #4	$15.57	11.810%	$17.4088	$17.41	$17.40	$17.40
Purchase #5	$53.27	5.153%	$56.015	$56.02	$56.00	$56.00
Purchase #6	$186.87	10.523%	$206.5343	$206.53	$206.55	$206.50
Purchase #7	$160.38	13.645%	$182.2639	$182.26	$182.25	$182.30
7 purchase totals =	$783.19		$868.1966	$868.20	$868.15	$868.20