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	$208.30	7.514%	$223.9517	$223.95	$223.95	$224.00
Purchase #2	$209.43	6.457%	$222.9529	$222.95	$222.95	$223.00
Purchase #3	$83.32	8.526%	$90.4239	$90.42	$90.40	$90.40
Purchase #4	$44.60	11.193%	$49.5921	$49.59	$49.60	$49.60
Purchase #5	$190.52	9.333%	$208.3012	$208.30	$208.30	$208.30
Purchase #6	$238.99	7.341%	$256.5343	$256.53	$256.55	$256.50
Purchase #7	$30.74	7.660%	$33.0947	$33.09	$33.10	$33.10
7 purchase totals =	$1,005.90		$1,084.8508	$1,084.83	$1,084.85	$1,084.90