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	$103.94	6.383%	$110.5745	$110.57	$110.55	$110.60
Purchase #2	$105.50	4.108%	$109.8339	$109.83	$109.85	$109.80
Purchase #3	$53.67	10.406%	$59.2549	$59.25	$59.25	$59.30
Purchase #4	$155.57	3.284%	$160.6789	$160.68	$160.70	$160.70
Purchase #5	$163.43	13.138%	$184.9014	$184.90	$184.90	$184.90
Purchase #6	$34.58	11.150%	$38.4357	$38.44	$38.45	$38.40
Purchase #7	$163.66	13.792%	$186.232	$186.23	$186.25	$186.20
7 purchase totals =	$780.35		$849.9113	$849.90	$849.95	$849.90