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	$164.86	13.104%	$186.4633	$186.46	$186.45	$186.50
Purchase #2	$39.84	11.253%	$44.3232	$44.32	$44.30	$44.30
Purchase #3	$57.61	7.648%	$62.016	$62.02	$62.00	$62.00
Purchase #4	$69.89	11.237%	$77.7435	$77.74	$77.75	$77.70
Purchase #5	$74.93	6.783%	$80.0125	$80.01	$80.00	$80.00
Purchase #6	$81.86	10.292%	$90.285	$90.29	$90.30	$90.30
Purchase #7	$12.92	8.528%	$14.0218	$14.02	$14.00	$14.00
7 purchase totals =	$501.91		$554.8653	$554.86	$554.80	$554.80