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	$102.76	13.587%	$116.722	$116.72	$116.70	$116.70
Purchase #2	$39.45	10.149%	$43.4538	$43.45	$43.45	$43.50
Purchase #3	$167.26	10.854%	$185.4144	$185.41	$185.40	$185.40
Purchase #4	$40.73	10.479%	$44.9981	$45.00	$45.00	$45.00
Purchase #5	$106.50	6.217%	$113.1211	$113.12	$113.10	$113.10
Purchase #6	$98.58	12.678%	$111.078	$111.08	$111.10	$111.10
Purchase #7	$152.52	7.805%	$164.4242	$164.42	$164.40	$164.40
7 purchase totals =	$707.80		$779.2116	$779.20	$779.15	$779.20