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	$114.43	11.367%	$127.4373	$127.44	$127.45	$127.40
Purchase #2	$60.82	9.651%	$66.6897	$66.69	$66.70	$66.70
Purchase #3	$185.99	11.144%	$206.7167	$206.72	$206.70	$206.70
Purchase #4	$179.58	9.658%	$196.9238	$196.92	$196.90	$196.90
Purchase #5	$24.73	12.237%	$27.7562	$27.76	$27.75	$27.80
Purchase #6	$226.95	3.379%	$234.6186	$234.62	$234.60	$234.60
Purchase #7	$226.35	6.659%	$241.4226	$241.42	$241.40	$241.40
7 purchase totals =	$1,018.85		$1,101.5649	$1,101.57	$1,101.50	$1,101.50