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	$88.31	4.841%	$92.5851	$92.59	$92.60	$92.60
Purchase #2	$113.77	12.260%	$127.7182	$127.72	$127.70	$127.70
Purchase #3	$241.93	7.822%	$260.8538	$260.85	$260.85	$260.90
Purchase #4	$154.27	8.672%	$167.6483	$167.65	$167.65	$167.60
Purchase #5	$240.95	7.335%	$258.6237	$258.62	$258.60	$258.60
Purchase #6	$177.39	11.531%	$197.8448	$197.84	$197.85	$197.80
Purchase #7	$56.63	4.762%	$59.3267	$59.33	$59.35	$59.30
7 purchase totals =	$1,073.25		$1,164.6006	$1,164.60	$1,164.60	$1,164.50