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	$175.95	5.641%	$185.8753	$185.88	$185.90	$185.90
Purchase #2	$61.38	6.819%	$65.5655	$65.57	$65.55	$65.60
Purchase #3	$32.91	5.176%	$34.6134	$34.61	$34.60	$34.60
Purchase #4	$102.54	9.264%	$112.0393	$112.04	$112.05	$112.00
Purchase #5	$34.55	5.151%	$36.3297	$36.33	$36.35	$36.30
Purchase #6	$6.27	3.758%	$6.5056	$6.51	$6.50	$6.50
Purchase #7	$80.89	12.103%	$90.6801	$90.68	$90.70	$90.70
7 purchase totals =	$494.49		$531.6089	$531.62	$531.65	$531.60