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	$58.29	11.789%	$65.1618	$65.16	$65.15	$65.20
Purchase #2	$61.71	6.402%	$65.6607	$65.66	$65.65	$65.70
Purchase #3	$232.68	9.538%	$254.873	$254.87	$254.85	$254.90
Purchase #4	$46.90	12.141%	$52.5941	$52.59	$52.60	$52.60
Purchase #5	$92.43	10.410%	$102.052	$102.05	$102.05	$102.10
Purchase #6	$121.84	5.378%	$128.3926	$128.39	$128.40	$128.40
Purchase #7	$88.35	12.683%	$99.5554	$99.56	$99.55	$99.60
7 purchase totals =	$702.20		$768.2896	$768.28	$768.25	$768.50