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	$132.79	7.146%	$142.2792	$142.28	$142.30	$142.30
Purchase #2	$37.33	4.178%	$38.8896	$38.89	$38.90	$38.90
Purchase #3	$144.93	6.204%	$153.9215	$153.92	$153.90	$153.90
Purchase #4	$68.53	11.351%	$76.3088	$76.31	$76.30	$76.30
Purchase #5	$76.43	7.566%	$82.2127	$82.21	$82.20	$82.20
Purchase #6	$101.25	10.392%	$111.7719	$111.77	$111.75	$111.80
Purchase #7	$65.65	7.703%	$70.707	$70.71	$70.70	$70.70
7 purchase totals =	$626.91		$676.0907	$676.09	$676.05	$676.10