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	$157.44	9.132%	$171.8174	$171.82	$171.80	$171.80
Purchase #2	$159.45	11.554%	$177.8729	$177.87	$177.85	$177.90
Purchase #3	$121.88	7.844%	$131.4403	$131.44	$131.45	$131.40
Purchase #4	$213.58	7.867%	$230.3823	$230.38	$230.40	$230.40
Purchase #5	$28.45	11.751%	$31.7932	$31.79	$31.80	$31.80
Purchase #6	$166.95	13.285%	$189.1293	$189.13	$189.15	$189.10
Purchase #7	$99.41	12.305%	$111.6424	$111.64	$111.65	$111.60
7 purchase totals =	$947.16		$1,044.0778	$1,044.07	$1,044.10	$1,044.00