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	$248.46	7.255%	$266.4858	$266.49	$266.50	$266.50
Purchase #2	$6.83	10.766%	$7.5653	$7.57	$7.55	$7.60
Purchase #3	$78.55	4.513%	$82.095	$82.10	$82.10	$82.10
Purchase #4	$165.52	3.599%	$171.4771	$171.48	$171.50	$171.50
Purchase #5	$40.81	10.822%	$45.2265	$45.23	$45.25	$45.20
Purchase #6	$233.66	10.186%	$257.4606	$257.46	$257.45	$257.50
Purchase #7	$206.51	11.386%	$230.0232	$230.02	$230.00	$230.00
7 purchase totals =	$980.34		$1,060.3335	$1,060.35	$1,060.35	$1,060.40