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	$123.95	5.436%	$130.6879	$130.69	$130.70	$130.70
Purchase #2	$81.44	6.320%	$86.587	$86.59	$86.60	$86.60
Purchase #3	$19.56	7.769%	$21.0796	$21.08	$21.10	$21.10
Purchase #4	$17.49	4.468%	$18.2715	$18.27	$18.25	$18.30
Purchase #5	$80.45	11.721%	$89.8795	$89.88	$89.90	$89.90
Purchase #6	$154.86	11.238%	$172.2632	$172.26	$172.25	$172.30
Purchase #7	$246.25	3.768%	$255.5287	$255.53	$255.55	$255.50
7 purchase totals =	$724.00		$774.2974	$774.30	$774.35	$774.40