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	$194.46	13.784%	$221.2644	$221.26	$221.25	$221.30
Purchase #2	$128.31	4.654%	$134.2815	$134.28	$134.30	$134.30
Purchase #3	$108.46	13.766%	$123.3906	$123.39	$123.40	$123.40
Purchase #4	$215.61	11.524%	$240.4569	$240.46	$240.45	$240.50
Purchase #5	$74.88	11.441%	$83.447	$83.45	$83.45	$83.40
Purchase #6	$170.96	13.748%	$194.4636	$194.46	$194.45	$194.50
Purchase #7	$197.54	11.182%	$219.6289	$219.63	$219.65	$219.60
7 purchase totals =	$1,090.22		$1,216.9329	$1,216.93	$1,216.95	$1,217.00