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	$30.68	5.672%	$32.4202	$32.42	$32.40	$32.40
Purchase #2	$125.84	13.552%	$142.8938	$142.89	$142.90	$142.90
Purchase #3	$19.68	7.695%	$21.1944	$21.19	$21.20	$21.20
Purchase #4	$208.54	3.253%	$215.3238	$215.32	$215.30	$215.30
Purchase #5	$54.61	8.822%	$59.4277	$59.43	$59.45	$59.40
Purchase #6	$178.64	9.763%	$196.0806	$196.08	$196.10	$196.10
Purchase #7	$189.60	6.272%	$201.4917	$201.49	$201.50	$201.50
7 purchase totals =	$807.59		$868.8322	$868.82	$868.85	$868.80