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	$34.52	11.671%	$38.5488	$38.55	$38.55	$38.50
Purchase #2	$132.71	5.433%	$139.9201	$139.92	$139.90	$139.90
Purchase #3	$73.56	5.678%	$77.7367	$77.74	$77.75	$77.70
Purchase #4	$235.33	13.650%	$267.4525	$267.45	$267.45	$267.50
Purchase #5	$141.55	6.844%	$151.2377	$151.24	$151.25	$151.20
Purchase #6	$101.67	4.154%	$105.8934	$105.89	$105.90	$105.90
Purchase #7	$164.75	10.481%	$182.0174	$182.02	$182.00	$182.00
7 purchase totals =	$884.09		$962.8066	$962.81	$962.80	$962.70