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	$127.72	3.384%	$132.042	$132.04	$132.05	$132.00
Purchase #2	$76.81	12.684%	$86.5526	$86.55	$86.55	$86.60
Purchase #3	$220.30	12.764%	$248.4191	$248.42	$248.40	$248.40
Purchase #4	$40.91	13.422%	$46.4009	$46.40	$46.40	$46.40
Purchase #5	$199.46	7.756%	$214.9301	$214.93	$214.95	$214.90
Purchase #6	$100.59	10.617%	$111.2696	$111.27	$111.25	$111.30
Purchase #7	$216.33	13.437%	$245.3983	$245.40	$245.40	$245.40
7 purchase totals =	$982.12		$1,085.0126	$1,085.01	$1,085.00	$1,085.00