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	$167.71	13.730%	$190.7366	$190.74	$190.75	$190.70
Purchase #2	$84.87	6.134%	$90.0759	$90.08	$90.10	$90.10
Purchase #3	$122.87	13.687%	$139.6872	$139.69	$139.70	$139.70
Purchase #4	$150.91	3.851%	$156.7215	$156.72	$156.70	$156.70
Purchase #5	$140.78	12.255%	$158.0326	$158.03	$158.05	$158.00
Purchase #6	$73.89	7.182%	$79.1968	$79.20	$79.20	$79.20
Purchase #7	$242.47	5.816%	$256.5721	$256.57	$256.55	$256.60
7 purchase totals =	$983.50		$1,071.0227	$1,071.03	$1,071.05	$1,071.00