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	$105.94	5.196%	$111.4446	$111.44	$111.45	$111.40
Purchase #2	$158.97	8.383%	$172.2965	$172.30	$172.30	$172.30
Purchase #3	$21.84	9.348%	$23.8816	$23.88	$23.90	$23.90
Purchase #4	$161.53	10.449%	$178.4083	$178.41	$178.40	$178.40
Purchase #5	$51.66	7.450%	$55.5087	$55.51	$55.50	$55.50
Purchase #6	$147.30	10.322%	$162.5043	$162.50	$162.50	$162.50
Purchase #7	$212.85	5.213%	$223.9459	$223.95	$223.95	$223.90
7 purchase totals =	$860.09		$927.9899	$927.99	$928.00	$927.90