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	$208.51	6.813%	$222.7158	$222.72	$222.70	$222.70
Purchase #2	$105.83	4.752%	$110.859	$110.86	$110.85	$110.90
Purchase #3	$203.95	11.227%	$226.8475	$226.85	$226.85	$226.80
Purchase #4	$156.88	6.130%	$166.4967	$166.50	$166.50	$166.50
Purchase #5	$9.53	5.626%	$10.0662	$10.07	$10.05	$10.10
Purchase #6	$85.69	3.601%	$88.7757	$88.78	$88.80	$88.80
Purchase #7	$236.33	11.576%	$263.6876	$263.69	$263.70	$263.70
7 purchase totals =	$1,006.72		$1,089.4485	$1,089.47	$1,089.45	$1,089.50