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	$221.60	5.485%	$233.7548	$233.75	$233.75	$233.80
Purchase #2	$136.95	3.680%	$141.9898	$141.99	$142.00	$142.00
Purchase #3	$156.83	9.725%	$172.0817	$172.08	$172.10	$172.10
Purchase #4	$73.64	12.470%	$82.8229	$82.82	$82.80	$82.80
Purchase #5	$19.91	6.722%	$21.2484	$21.25	$21.25	$21.20
Purchase #6	$126.92	3.656%	$131.5602	$131.56	$131.55	$131.60
Purchase #7	$156.28	11.696%	$174.5585	$174.56	$174.55	$174.60
7 purchase totals =	$892.13		$958.0163	$958.01	$958.00	$958.10