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	$119.78	6.509%	$127.5765	$127.58	$127.60	$127.60
Purchase #2	$201.83	5.810%	$213.5563	$213.56	$213.55	$213.60
Purchase #3	$128.58	4.548%	$134.4278	$134.43	$134.45	$134.40
Purchase #4	$100.88	3.842%	$104.7558	$104.76	$104.75	$104.80
Purchase #5	$222.65	6.580%	$237.3004	$237.30	$237.30	$237.30
Purchase #6	$226.25	8.543%	$245.5785	$245.58	$245.60	$245.60
Purchase #7	$25.41	9.104%	$27.7233	$27.72	$27.70	$27.70
7 purchase totals =	$1,025.38		$1,090.9186	$1,090.93	$1,090.95	$1,091.00