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	$145.67	3.372%	$150.582	$150.58	$150.60	$150.60
Purchase #2	$72.56	9.420%	$79.3952	$79.40	$79.40	$79.40
Purchase #3	$226.39	3.625%	$234.5966	$234.60	$234.60	$234.60
Purchase #4	$30.72	9.411%	$33.6111	$33.61	$33.60	$33.60
Purchase #5	$137.76	10.136%	$151.7234	$151.72	$151.70	$151.70
Purchase #6	$34.43	12.684%	$38.7971	$38.80	$38.80	$38.80
Purchase #7	$29.86	4.304%	$31.1452	$31.15	$31.15	$31.10
7 purchase totals =	$677.39		$719.8506	$719.86	$719.85	$719.80