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	$239.71	5.536%	$252.9803	$252.98	$253.00	$253.00
Purchase #2	$80.74	9.762%	$88.6218	$88.62	$88.60	$88.60
Purchase #3	$120.91	9.112%	$131.9273	$131.93	$131.95	$131.90
Purchase #4	$111.69	5.551%	$117.8899	$117.89	$117.90	$117.90
Purchase #5	$155.47	5.597%	$164.1717	$164.17	$164.15	$164.20
Purchase #6	$224.30	10.861%	$248.6612	$248.66	$248.65	$248.70
Purchase #7	$18.62	12.199%	$20.8915	$20.89	$20.90	$20.90
7 purchase totals =	$951.44		$1,025.1437	$1,025.14	$1,025.15	$1,025.20