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	$220.88	12.527%	$248.5496	$248.55	$248.55	$248.50
Purchase #2	$68.28	11.275%	$75.9786	$75.98	$76.00	$76.00
Purchase #3	$7.69	7.621%	$8.2761	$8.28	$8.30	$8.30
Purchase #4	$201.44	12.403%	$226.4246	$226.42	$226.40	$226.40
Purchase #5	$82.94	7.605%	$89.2476	$89.25	$89.25	$89.20
Purchase #6	$235.71	5.580%	$248.8626	$248.86	$248.85	$248.90
Purchase #7	$145.95	12.788%	$164.6141	$164.61	$164.60	$164.60
7 purchase totals =	$962.89		$1,061.9532	$1,061.95	$1,061.95	$1,061.90