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	$221.81	13.544%	$251.8519	$251.85	$251.85	$251.90
Purchase #2	$159.44	3.474%	$164.9789	$164.98	$165.00	$165.00
Purchase #3	$53.82	9.773%	$59.0798	$59.08	$59.10	$59.10
Purchase #4	$238.98	7.493%	$256.8868	$256.89	$256.90	$256.90
Purchase #5	$65.40	7.636%	$70.3939	$70.39	$70.40	$70.40
Purchase #6	$102.41	3.438%	$105.9309	$105.93	$105.95	$105.90
Purchase #7	$136.60	7.757%	$147.1961	$147.20	$147.20	$147.20
7 purchase totals =	$978.46		$1,056.3183	$1,056.32	$1,056.40	$1,056.40