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	$212.75	4.839%	$223.045	$223.05	$223.05	$223.00
Purchase #2	$222.30	3.665%	$230.4473	$230.45	$230.45	$230.40
Purchase #3	$73.87	11.685%	$82.5017	$82.50	$82.50	$82.50
Purchase #4	$215.59	3.156%	$222.394	$222.39	$222.40	$222.40
Purchase #5	$65.48	10.861%	$72.5918	$72.59	$72.60	$72.60
Purchase #6	$32.91	3.172%	$33.9539	$33.95	$33.95	$34.00
Purchase #7	$249.37	5.602%	$263.3397	$263.34	$263.35	$263.30
7 purchase totals =	$1,072.27		$1,128.2734	$1,128.27	$1,128.30	$1,128.20