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	$130.52	10.710%	$144.4987	$144.50	$144.50	$144.50
Purchase #2	$249.43	6.852%	$266.5209	$266.52	$266.50	$266.50
Purchase #3	$140.31	11.152%	$155.9574	$155.96	$155.95	$156.00
Purchase #4	$158.30	11.255%	$176.1167	$176.12	$176.10	$176.10
Purchase #5	$71.73	11.273%	$79.8161	$79.82	$79.80	$79.80
Purchase #6	$174.47	12.636%	$196.516	$196.52	$196.50	$196.50
Purchase #7	$31.95	11.645%	$35.6706	$35.67	$35.65	$35.70
7 purchase totals =	$956.71		$1,055.0964	$1,055.11	$1,055.00	$1,055.10