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	$194.61	11.308%	$216.6165	$216.62	$216.60	$216.60
Purchase #2	$238.35	8.248%	$258.0091	$258.01	$258.00	$258.00
Purchase #3	$95.92	12.482%	$107.8927	$107.89	$107.90	$107.90
Purchase #4	$116.32	9.558%	$127.4379	$127.44	$127.45	$127.40
Purchase #5	$59.47	5.277%	$62.6082	$62.61	$62.60	$62.60
Purchase #6	$38.79	9.758%	$42.5751	$42.58	$42.60	$42.60
Purchase #7	$137.41	7.252%	$147.375	$147.38	$147.40	$147.40
7 purchase totals =	$880.87		$962.5145	$962.53	$962.55	$962.50