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	$242.98	4.675%	$254.3393	$254.34	$254.35	$254.30
Purchase #2	$57.54	9.204%	$62.836	$62.84	$62.85	$62.80
Purchase #3	$133.41	6.782%	$142.4579	$142.46	$142.45	$142.50
Purchase #4	$87.54	3.684%	$90.765	$90.77	$90.75	$90.80
Purchase #5	$13.70	6.370%	$14.5727	$14.57	$14.55	$14.60
Purchase #6	$125.48	5.161%	$131.956	$131.96	$131.95	$132.00
Purchase #7	$153.83	11.394%	$171.3574	$171.36	$171.35	$171.40
7 purchase totals =	$814.48		$868.2843	$868.30	$868.25	$868.40