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	$105.64	5.744%	$111.708	$111.71	$111.70	$111.70
Purchase #2	$109.93	7.133%	$117.7713	$117.77	$117.75	$117.80
Purchase #3	$200.88	11.257%	$223.4931	$223.49	$223.50	$223.50
Purchase #4	$164.30	13.781%	$186.9422	$186.94	$186.95	$186.90
Purchase #5	$114.30	11.547%	$127.4982	$127.50	$127.50	$127.50
Purchase #6	$106.41	12.379%	$119.5825	$119.58	$119.60	$119.60
Purchase #7	$191.93	3.105%	$197.8894	$197.89	$197.90	$197.90
7 purchase totals =	$993.39		$1,084.8847	$1,084.88	$1,084.90	$1,084.90