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	$43.32	9.758%	$47.5472	$47.55	$47.55	$47.50
Purchase #2	$181.81	3.323%	$187.8515	$187.85	$187.85	$187.90
Purchase #3	$101.82	11.482%	$113.511	$113.51	$113.50	$113.50
Purchase #4	$180.94	11.820%	$202.3271	$202.33	$202.35	$202.30
Purchase #5	$127.92	10.557%	$141.4245	$141.42	$141.40	$141.40
Purchase #6	$222.43	9.526%	$243.6187	$243.62	$243.60	$243.60
Purchase #7	$155.47	5.397%	$163.8607	$163.86	$163.85	$163.90
7 purchase totals =	$1,013.71		$1,100.1407	$1,100.14	$1,100.10	$1,100.10