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	$101.97	3.594%	$105.6348	$105.63	$105.65	$105.60
Purchase #2	$104.36	9.404%	$114.174	$114.17	$114.15	$114.20
Purchase #3	$110.47	6.448%	$117.5931	$117.59	$117.60	$117.60
Purchase #4	$66.49	12.703%	$74.9362	$74.94	$74.95	$74.90
Purchase #5	$98.34	13.481%	$111.5972	$111.60	$111.60	$111.60
Purchase #6	$127.48	13.761%	$145.0225	$145.02	$145.00	$145.00
Purchase #7	$30.62	3.618%	$31.7278	$31.73	$31.75	$31.70
7 purchase totals =	$639.73		$700.6856	$700.68	$700.70	$700.60