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	$241.66	9.348%	$264.2504	$264.25	$264.25	$264.30
Purchase #2	$239.78	8.446%	$260.0318	$260.03	$260.05	$260.00
Purchase #3	$36.43	10.236%	$40.159	$40.16	$40.15	$40.20
Purchase #4	$40.81	10.697%	$45.1754	$45.18	$45.20	$45.20
Purchase #5	$99.67	5.558%	$105.2097	$105.21	$105.20	$105.20
Purchase #6	$35.98	11.259%	$40.031	$40.03	$40.05	$40.00
Purchase #7	$43.45	10.703%	$48.1005	$48.10	$48.10	$48.10
7 purchase totals =	$737.78		$802.9578	$802.96	$803.00	$803.00