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	8.426%	$98.234	$98.23	$98.25	$98.20
Purchase #2	$137.33	4.394%	$143.3643	$143.36	$143.35	$143.40
Purchase #3	$18.77	10.591%	$20.7579	$20.76	$20.75	$20.80
Purchase #4	$108.87	6.632%	$116.0903	$116.09	$116.10	$116.10
Purchase #5	$158.57	6.857%	$169.4431	$169.44	$169.45	$169.40
Purchase #6	$224.55	13.336%	$254.496	$254.50	$254.50	$254.50
Purchase #7	$58.48	12.113%	$65.5637	$65.56	$65.55	$65.60
7 purchase totals =	$797.17		$867.9493	$867.94	$867.95	$868.00