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	$182.83	10.622%	$202.2502	$202.25	$202.25	$202.30
Purchase #2	$143.72	6.767%	$153.4455	$153.45	$153.45	$153.40
Purchase #3	$98.84	10.427%	$109.146	$109.15	$109.15	$109.10
Purchase #4	$55.96	5.665%	$59.1301	$59.13	$59.15	$59.10
Purchase #5	$162.95	3.747%	$169.0557	$169.06	$169.05	$169.10
Purchase #6	$79.89	11.504%	$89.0805	$89.08	$89.10	$89.10
Purchase #7	$98.75	11.390%	$109.9976	$110.00	$110.00	$110.00
7 purchase totals =	$822.94		$892.1056	$892.12	$892.15	$892.10