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	$159.95	10.106%	$176.1145	$176.11	$176.10	$176.10
Purchase #2	$65.67	3.324%	$67.8529	$67.85	$67.85	$67.90
Purchase #3	$112.97	4.464%	$118.013	$118.01	$118.00	$118.00
Purchase #4	$145.72	3.718%	$151.1379	$151.14	$151.15	$151.10
Purchase #5	$243.67	9.254%	$266.2192	$266.22	$266.20	$266.20
Purchase #6	$83.86	3.142%	$86.4949	$86.49	$86.50	$86.50
Purchase #7	$131.31	6.240%	$139.5037	$139.50	$139.50	$139.50
7 purchase totals =	$943.15		$1,005.3361	$1,005.32	$1,005.30	$1,005.30