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	$171.33	9.212%	$187.1129	$187.11	$187.10	$187.10
Purchase #2	$103.31	8.405%	$111.9932	$111.99	$112.00	$112.00
Purchase #3	$229.31	9.333%	$250.7115	$250.71	$250.70	$250.70
Purchase #4	$233.47	3.337%	$241.2609	$241.26	$241.25	$241.30
Purchase #5	$166.43	11.623%	$185.7742	$185.77	$185.75	$185.80
Purchase #6	$114.31	3.488%	$118.2971	$118.30	$118.30	$118.30
Purchase #7	$95.95	5.214%	$100.9528	$100.95	$100.95	$101.00
7 purchase totals =	$1,114.11		$1,196.1026	$1,196.09	$1,196.05	$1,196.20