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	$102.49	3.646%	$106.2268	$106.23	$106.25	$106.20
Purchase #2	$132.89	10.177%	$146.4142	$146.41	$146.40	$146.40
Purchase #3	$107.54	3.469%	$111.2706	$111.27	$111.25	$111.30
Purchase #4	$41.96	12.789%	$47.3263	$47.33	$47.35	$47.30
Purchase #5	$159.60	9.592%	$174.9088	$174.91	$174.90	$174.90
Purchase #6	$172.51	6.402%	$183.5541	$183.55	$183.55	$183.60
Purchase #7	$212.72	6.726%	$227.0275	$227.03	$227.05	$227.00
7 purchase totals =	$929.71		$996.7283	$996.73	$996.75	$996.70