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	$56.99	3.682%	$59.0884	$59.09	$59.10	$59.10
Purchase #2	$154.34	10.691%	$170.8405	$170.84	$170.85	$170.80
Purchase #3	$250.30	6.388%	$266.2892	$266.29	$266.30	$266.30
Purchase #4	$219.95	8.418%	$238.4654	$238.47	$238.45	$238.50
Purchase #5	$221.83	7.538%	$238.5515	$238.55	$238.55	$238.60
Purchase #6	$174.86	7.848%	$188.583	$188.58	$188.60	$188.60
Purchase #7	$110.85	3.126%	$114.3152	$114.32	$114.30	$114.30
7 purchase totals =	$1,189.12		$1,276.1332	$1,276.14	$1,276.15	$1,276.20