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	$240.75	3.581%	$249.3713	$249.37	$249.35	$249.40
Purchase #2	$123.60	10.648%	$136.7609	$136.76	$136.75	$136.80
Purchase #3	$92.59	9.641%	$101.5166	$101.52	$101.50	$101.50
Purchase #4	$170.27	10.636%	$188.3799	$188.38	$188.40	$188.40
Purchase #5	$240.52	6.604%	$256.4039	$256.40	$256.40	$256.40
Purchase #6	$223.87	3.105%	$230.8212	$230.82	$230.80	$230.80
Purchase #7	$56.27	13.837%	$64.0561	$64.06	$64.05	$64.10
7 purchase totals =	$1,147.87		$1,227.3099	$1,227.31	$1,227.25	$1,227.40