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	$154.78	8.488%	$167.9177	$167.92	$167.90	$167.90
Purchase #2	$83.76	6.788%	$89.4456	$89.45	$89.45	$89.40
Purchase #3	$136.82	4.584%	$143.0918	$143.09	$143.10	$143.10
Purchase #4	$14.35	7.524%	$15.4297	$15.43	$15.45	$15.40
Purchase #5	$94.49	9.127%	$103.1141	$103.11	$103.10	$103.10
Purchase #6	$44.84	11.455%	$49.9764	$49.98	$50.00	$50.00
Purchase #7	$184.39	4.616%	$192.9014	$192.90	$192.90	$192.90
7 purchase totals =	$713.43		$761.8767	$761.88	$761.90	$761.80