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	$47.29	12.762%	$53.3251	$53.33	$53.35	$53.30
Purchase #2	$219.81	12.147%	$246.5103	$246.51	$246.50	$246.50
Purchase #3	$57.89	8.129%	$62.5959	$62.60	$62.60	$62.60
Purchase #4	$225.62	12.153%	$253.0396	$253.04	$253.05	$253.00
Purchase #5	$69.49	11.406%	$77.416	$77.42	$77.40	$77.40
Purchase #6	$153.90	6.587%	$164.0374	$164.04	$164.05	$164.00
Purchase #7	$173.95	6.304%	$184.9158	$184.92	$184.90	$184.90
7 purchase totals =	$947.95		$1,041.8401	$1,041.86	$1,041.85	$1,041.70