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	$57.42	7.314%	$61.6197	$61.62	$61.60	$61.60
Purchase #2	$85.46	3.309%	$88.2879	$88.29	$88.30	$88.30
Purchase #3	$136.35	12.711%	$153.6814	$153.68	$153.70	$153.70
Purchase #4	$89.49	13.392%	$101.4745	$101.47	$101.45	$101.50
Purchase #5	$89.93	5.317%	$94.7116	$94.71	$94.70	$94.70
Purchase #6	$20.61	6.154%	$21.8783	$21.88	$21.90	$21.90
Purchase #7	$143.39	9.384%	$156.8457	$156.85	$156.85	$156.80
7 purchase totals =	$622.65		$678.4991	$678.50	$678.50	$678.50