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	$26.59	10.696%	$29.4341	$29.43	$29.45	$29.40
Purchase #2	$75.64	9.342%	$82.7063	$82.71	$82.70	$82.70
Purchase #3	$176.33	9.371%	$192.8539	$192.85	$192.85	$192.90
Purchase #4	$245.37	4.172%	$255.6068	$255.61	$255.60	$255.60
Purchase #5	$55.41	13.246%	$62.7496	$62.75	$62.75	$62.70
Purchase #6	$64.27	3.148%	$66.2932	$66.29	$66.30	$66.30
Purchase #7	$182.44	7.222%	$195.6158	$195.62	$195.60	$195.60
7 purchase totals =	$826.05		$885.2597	$885.26	$885.25	$885.20