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	$150.27	4.265%	$156.679	$156.68	$156.70	$156.70
Purchase #2	$119.77	6.481%	$127.5323	$127.53	$127.55	$127.50
Purchase #3	$201.32	10.569%	$222.5975	$222.60	$222.60	$222.60
Purchase #4	$42.79	13.412%	$48.529	$48.53	$48.55	$48.50
Purchase #5	$194.64	12.162%	$218.3121	$218.31	$218.30	$218.30
Purchase #6	$236.30	11.490%	$263.4509	$263.45	$263.45	$263.50
Purchase #7	$117.88	12.766%	$132.9286	$132.93	$132.95	$132.90
7 purchase totals =	$1,062.97		$1,170.0294	$1,170.03	$1,170.10	$1,170.00