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	$59.48	10.682%	$65.8337	$65.83	$65.85	$65.80
Purchase #2	$225.83	8.576%	$245.1972	$245.20	$245.20	$245.20
Purchase #3	$170.92	8.126%	$184.809	$184.81	$184.80	$184.80
Purchase #4	$40.51	5.812%	$42.8644	$42.86	$42.85	$42.90
Purchase #5	$153.67	11.839%	$171.863	$171.86	$171.85	$171.90
Purchase #6	$59.31	5.523%	$62.5857	$62.59	$62.60	$62.60
Purchase #7	$164.43	7.355%	$176.5238	$176.52	$176.50	$176.50
7 purchase totals =	$874.15		$949.6768	$949.67	$949.65	$949.70