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	$51.69	8.754%	$56.2149	$56.21	$56.20	$56.20
Purchase #2	$150.52	7.739%	$162.1687	$162.17	$162.15	$162.20
Purchase #3	$210.66	3.741%	$218.5408	$218.54	$218.55	$218.50
Purchase #4	$228.39	9.641%	$250.4091	$250.41	$250.40	$250.40
Purchase #5	$248.36	5.610%	$262.293	$262.29	$262.30	$262.30
Purchase #6	$67.36	5.333%	$70.9523	$70.95	$70.95	$71.00
Purchase #7	$179.49	9.221%	$196.0408	$196.04	$196.05	$196.00
7 purchase totals =	$1,136.47		$1,216.6196	$1,216.61	$1,216.60	$1,216.60