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	$77.37	8.496%	$83.9434	$83.94	$83.95	$83.90
Purchase #2	$86.57	4.663%	$90.6068	$90.61	$90.60	$90.60
Purchase #3	$56.37	3.621%	$58.4112	$58.41	$58.40	$58.40
Purchase #4	$196.49	9.649%	$215.4493	$215.45	$215.45	$215.40
Purchase #5	$227.57	10.309%	$251.0302	$251.03	$251.05	$251.00
Purchase #6	$21.39	13.108%	$24.1938	$24.19	$24.20	$24.20
Purchase #7	$200.25	4.690%	$209.6417	$209.64	$209.65	$209.60
7 purchase totals =	$866.01		$933.2764	$933.27	$933.30	$933.10