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	$61.44	6.548%	$65.4631	$65.46	$65.45	$65.50
Purchase #2	$9.97	5.648%	$10.5331	$10.53	$10.55	$10.50
Purchase #3	$233.58	13.166%	$264.3331	$264.33	$264.35	$264.30
Purchase #4	$55.99	3.161%	$57.7598	$57.76	$57.75	$57.80
Purchase #5	$243.81	4.836%	$255.6007	$255.60	$255.60	$255.60
Purchase #6	$70.78	11.517%	$78.9317	$78.93	$78.95	$78.90
Purchase #7	$239.59	9.593%	$262.5739	$262.57	$262.55	$262.60
7 purchase totals =	$915.16		$995.1954	$995.18	$995.20	$995.20