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	$90.60	13.494%	$102.8256	$102.83	$102.85	$102.80
Purchase #2	$20.26	11.524%	$22.5948	$22.59	$22.60	$22.60
Purchase #3	$55.69	12.420%	$62.6067	$62.61	$62.60	$62.60
Purchase #4	$148.68	13.261%	$168.3965	$168.40	$168.40	$168.40
Purchase #5	$112.96	12.647%	$127.2461	$127.25	$127.25	$127.20
Purchase #6	$36.75	3.806%	$38.1487	$38.15	$38.15	$38.10
Purchase #7	$56.71	3.484%	$58.6858	$58.69	$58.70	$58.70
7 purchase totals =	$521.65		$580.5042	$580.52	$580.55	$580.40