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	$10.39	10.357%	$11.4661	$11.47	$11.45	$11.50
Purchase #2	$147.60	11.314%	$164.2995	$164.30	$164.30	$164.30
Purchase #3	$72.35	10.329%	$79.823	$79.82	$79.80	$79.80
Purchase #4	$125.40	5.408%	$132.1816	$132.18	$132.20	$132.20
Purchase #5	$34.95	11.433%	$38.9458	$38.95	$38.95	$38.90
Purchase #6	$171.64	13.497%	$194.8063	$194.81	$194.80	$194.80
Purchase #7	$122.45	4.134%	$127.5121	$127.51	$127.50	$127.50
7 purchase totals =	$684.78		$749.0344	$749.04	$749.00	$749.00