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	$182.37	4.544%	$190.6569	$190.66	$190.65	$190.70
Purchase #2	$29.71	4.364%	$31.0065	$31.01	$31.00	$31.00
Purchase #3	$155.39	9.119%	$169.56	$169.56	$169.55	$169.60
Purchase #4	$58.82	9.647%	$64.4944	$64.49	$64.50	$64.50
Purchase #5	$64.53	4.262%	$67.2803	$67.28	$67.30	$67.30
Purchase #6	$163.62	13.291%	$185.3667	$185.37	$185.35	$185.40
Purchase #7	$145.88	8.716%	$158.5949	$158.59	$158.60	$158.60
7 purchase totals =	$800.32		$866.9597	$866.96	$866.95	$867.10