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	$142.82	11.389%	$159.0858	$159.09	$159.10	$159.10
Purchase #2	$105.54	3.317%	$109.0408	$109.04	$109.05	$109.00
Purchase #3	$79.69	12.556%	$89.6959	$89.70	$89.70	$89.70
Purchase #4	$242.34	5.544%	$255.7753	$255.78	$255.80	$255.80
Purchase #5	$223.69	8.321%	$242.3032	$242.30	$242.30	$242.30
Purchase #6	$117.64	4.206%	$122.5879	$122.59	$122.60	$122.60
Purchase #7	$126.64	4.725%	$132.6237	$132.62	$132.60	$132.60
7 purchase totals =	$1,038.36		$1,111.1126	$1,111.12	$1,111.15	$1,111.10